If you haven’t been living under a rock since the R5 was released I’d say you already know how widespread this is. The definition of widespread is when Canon releases a firmware to fix it, and use the phrase “in rare cases”.
I don't know what threshold Canon has for responding with a FW update, but, you are right, they took the complaints seriously enough to target the freezing/lockups with a minor update.
But the same posters who complained before 1.5.1 are complaining after it. I'm not sure Canon engineers even knew what they were trying to fix. It seems the variables and the combinations of possible culprits is approaching infinity.
So, my understanding is that your definition of "widespread" is a problem addressed by a FW update. Fair enough, but I'm still curious about the percentages. Supply chain issues may have resulted in some willingness by Canon to go with new sources for parts, and no matter how well engineered or programmed the R5 is, a part that is slightly dodgy, combined with memory cards that are also seeing new sources of parts, and Canon and aftermarket batteries that might or might not be involved...
Fortunately, the problem is not affecting me. That's all I can say with certainty regarding R5 lockups. And I can say with certainty I haven't had any of the AF troubles you've had with pretty much every camera you've had. This should not, however, make me blind or insensitive to the problems others are having.
I'm also curious about whether other brands are going through similar cycles of elusive issues.