Yes I had the same issue. Problem I saw was G-Sight does not sell a replacement rear pad for the Gen 3. I looked everywhere. Finally I found LaserHIT which sold end caps. I ordered it and it now works fine. Here's the link:I have been using the G-Sight system and love it. I have run into an issue in which the dimple has grown and now it will not activate the laser. I switched it around to different pistols, but it is still having difficulty with the FN 509 C MRD. Curious if anyone else has run into issues.
REPLACEABLE CAP/KIT (2021 edition) — LaserHIT - Modern Firearm Training at Home