From time to time I encounter incorrectly working v-if. What's the matter?

Question

Vue.js

Several times recently I ran into an incorrectly working v-if. It is difficult to give an example, because all of them in a very fancy context to be shown in public.
But the thing is that the conditional block is not shown on the screen, as if its v-if value is FALSE. I copy-paste the conditions from v-if to the console, and in black and white I see that it is TRUE. Satan!
I noticed that this happens with fancy conditions of 3-4-5 operands, or if the c v-if block itself is inside another block with v-if.
I find it difficult to formulate the question, I’ll ask not quite specifically: Maybe I don’t understand something in the work of v-if? Are there any pitfalls in v-if "widely known in narrow circles of limited persons"?