If it was some memory corruption, I'd expect that you encounter strange
problems and crashes with more important applications, e.g., crashes of
X, kernel oops, etc.
Not really. Most of the run-of-the-mill applications don't react all
that much to the occasionally flipping bit.
I had once debugged a problem for hours in a program of mine until
finding the problem. When doing arithmetic right shifts of negative
numbers, the sign randomly became positive. Exchanged the processor,
problem gone. Apart from causing this one program to malfunction, there
was no previous sighting of any problems, likely for years.
Similar with the systems that were not able to finish several hours of
kernel compilation. No other signs of problems specific enough to
warrant attention.