Why won't the OS boot?

Question

HP

Good day. I am a necrophiliac and need help.
We have - HP t5740 Thin Client. The task is to install Ubuntu Server 16.04 x32
The disk is connected via an adapter to a sata connector (the adapter is working, the disks work with it on other PCs), the flash disk (included in the kit) is removed, the BIOS is reset, the disk is seen and detected. (Different disks were tried)
Problem - after installing the OS, at boot, after GRUB Menu - black screen with a flashing bar. Or just a black screen, with a different RAM chip.

More detailed info. We take from one seller (yes, all BUs, of course) this is not the first time these machines, for our tasks (play background music). 2 times they took large batches, everything was ok, they worked flawlessly - they pulled out the flash, connected the ssd through the "extension cable" sata + power (the connector is simply located "up" for some reason), ubuntu server 16 took off and worked perfectly (and right now 100 pieces plow on objects).
A couple of days ago we bought more, and for some reason we have a problem that is indicated at the beginning of the post ... despite the fact that the PC, disks, RAM, adapters are all the same ....

Help someone with what they can) the problem is only in the last batch and on all 15 PCs .... unclear