This is what we know:
(1) The desktop has a file corruption issue. The laptops do not. Accordingly, the issue is confined to your desktop.
(2) You did a fresh install of Solus, so it is unlikely that Solus is causing the problem on the desktop.
(3) Based on the symptoms, the most likely cause of the problem was a failing HHD. You replaced the HHD with an SSD. That did not resolve the problem.
Now you have to look further.
The next most likely causes of the problem are:
(1) A bad cable connecting the motherboard socket to the SSD.
(2) A bad motherboard socket used to connect to the SSD.
(3) A bad controller on the motherboard or another motherboard issue.
I suggest these steps:
(1) Move the cable connecting the motherboard to the SSD from the socket that it is now using to another socket. Typically, desktop motherboards have several sockets in a row, numbered "0" to whatever, and the booting HHD/SSD is connected to Socket 0. Move the cable connection from Socket 0 to the next socket down the line, probably Socket 1. That doesn't cost anything, and it is worth a try. See if that resolves the issue.
(2) If changing the socket does not solve the problem, then try replacing the cable connecting the motherboard socket to the SSD.
(3) If you are still getting file corruption at that point (new SSD, socket change, new cable, problem not solved), then you probably have a motherboard issue. Computer repair shops typically have the tools to test motherboards and diagnose problems, but it is likely that a shop would recommend replacing the motherboard if they find an issue. That's not trivial and you'll have to make a decision about whether to replace the motherboard or replace the old computer. Old computers are like old cars; you can keep them running almost forever, but after a certain point, it is more trouble than it is worth.