I had a used Bessa L that I got as part of a lens deal and it worked without problem for seven years. It was my main carry camera, other than on vacations where it was backup and the offical 25mm lens cap. Judging from what I expect to be the number made I'm not too sure what we are seeing is a few of thousands good ones.
I have heard of R's having issues with something jamming in the advance, but as I remember it was an easy fix taking off the bottom plate. More from a drop than anything else as I remember.
You might want to join the CVUG (CV User Group) from CameraQuest.com. I've been on it for years and it has lots of knowledge specific to Bessas but also beyond. There are lots of potential issues, people passing problematic cameras along to others. I never heard back from either of the two people I sold my Ls to.
I'm sure you will be fine with the L, my favorite street/family/fun film camera ever built, at least IMHO. Don't worry, treat her with respect and put lots of film through her.
And of course share your results and impressions with us!
B2