I have heard of that issue. Oddly, never from someone that actually owned one but I am sure 50+ people will chime in and tell me I am wrong.

JJ told me if it ever happened (I asked him about it) just put a drop of low strength loctite or clear fingernail polish on top of the screws.
The 141 in 9,3x74R has a learning curve to shoot well because it is so light. I had to get a good recoil pad for mine and put in a lot of patient, range time. I suspect that might be part of the issue for "losing regulation" as well as barrels heating quickly. At first, I was ready to send mine down the road I was so frustrated with it. Then someone with more double rifle experience and patience reached out and helped me.
I have had no issues with mine after getting to know it better and I have killed quite a bit of game in the US and Africa at distances out to just over 200 yards. (but most has been at 50 yards or less) It was my first double and the only one I have kept. However, were I to get another small bore double it would be a Chapuis because of Merkel's historical lack of interest in customer service. Also, JJ services Chapuis.
Safe shooting