How to safely terminate a fixed price contract?

Question

Upwork

Good afternoon. I had a not very pleasant situation. I took a fixed-price ($3850) contract. The contract consisted of 3 milestones (more precisely, it didn’t, but I stood on it)
1) Completion of an existing project, $ 300. - I did it, I received the payment, with the upwork I brought it out
2) Describe a couple of APIEndpoints for the second project - $50. I did the same, and received the money (but did not withdraw)
3) Implementation of a new project, for the remaining amount.
In general, I completed the first 2 points, as described above, after which the customer disappeared for more than 2 months, without leaving a detailed technical specification, site design, etc.
Showed up about a week ago.
I started asking for help with the second project, since the project does not work according to my endpoint documentation. I tried to explain to him that it's not the documentation, but the fact that these are bugs in the project itself.
(I’ll clarify a little, I wrote the docks on a part of the project that was not even compiled, the customer didn’t give the project completely, there was no access to the database either, there was also no access to the test project.)
I tried to get a working project from him again for verification suddenly all the same, I screwed up in the documentation, which was refused.
True, a couple of days later, when he realized that I could not help like that, he sent me a part of the project that was not going to, and there was also no access to any database. I honestly tried to build it by hand, delivering all the dependencies and so on. But just as unsuccessfully, half of the files were missing. I told the customer about this, to which he began to assure that this was a complete project. I gave him several examples that he was lying (the project was in C # and had * .csproj in which links to other projects, files, etc. are easily found).
Now he constantly asks me to look at the source codes and say what is written there, such as help to figure it out. P I'm already tired of it and I want to somehow abandon the project. Moreover, he writes at any time and in all chats: Skype, Slack and Upwork, mail. I tried to explain to him that at 3 am I sleep, but I don’t care. And also there is no question of any payment for this.
Well, actually the question is, how can I abandon this project with less losses? I am new to Upwork (I have 3 completed works and two of them with reviews - 4.7, 5).
Update0. Yes, on the second mailstone, I already thought about the adequacy of the customer, but I thought that it would blow over.
Update1. When I found out why he disappeared and what we will do with the project (3 milestone), he is silent and ignores.
update2. The client has a lot of good reviews (fives), but there are also bad ones that describe situations similar to mine, + blackmail is mentioned. I haven't gotten to blackmail yet.

Answer 1

a typical situation with fixed price contracts, there will be a lesson for you, you should never take fixed price contracts, even for a 5-minute "refinement" - sooner or later you will run into such a customer because of a penny edit that will ruin your reputation.
Of course, not everyone is so problematic, but in case of problems (for example, the client wants to endlessly stretch the volume of work, tightening and composating the brains as in the example), then you will always be extreme.
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There are not so many options:
1. money back (safe, but you lose money for the work already done)
2. Do not break the contract, it’s just that he also endlessly composes brains, he sends you something, you agree to look (but you don’t indicate the exact dates when you look at something or fix it), you just say all the time that you haven’t figured it out yet, it takes time, at the same time, you are never rude and DO NOT refuse work, you just drag out endless time, doing nothing, if he begins to express dissatisfaction with the expectation, you offer him to change the contractor.
The client will either terminate the contract himself, or will score, well, in which case it will be easier to resolve the dispute, all the same, the client himself disappeared, and now he does not want to wait until you have free time. . .
3. Try to bring everything to the state desired by the client - but I will assume that most likely it will not work out no matter how much work you put in, (you need to understand that the remaining 10% of the project always takes 90% of the work), those who order by fixed price often do not understand this and that- then it’s usually useless to explain to him (therefore, taking projects for a fix price is crazy, it’s good that you still had the mind to divide the project into stages, so you wouldn’t see a penny for your work).

Answer 2

Do you think that person does not understand what he is doing? He perfectly understands and uses you.
You have 2 cheap stages there, make a return and cancel the order. + prepare screenshots and competent proof in advance, because the customer can file complaints out of revenge, like you broke everything for him.

Answer 3

If it is not possible to agree with the client, then it is usually tedious to write to the support

Answer 4

update2. The client has a lot of good reviews (fives), but there are also bad ones that describe situations similar to mine, + blackmail is mentioned. I haven't gotten to blackmail yet.
it was with this that it was necessary to start, did they not study these reviews in advance or did they think that it would carry over?
Since you’ve already “stumbled” with a problematic client (and there are a lot of them, especially people from India or other sunny countries nearby) and you don’t want to spoil your turnips or there’s still no way to delete 1 negative review, then it remains to try to look for some kind of compromise, like something then he once again urgently needs to ask politely to close the project first with a normal response, then only do it, somehow, as diplomatically as possible, etc.