MPX cold weather issue?

MPX K, gen 3 Bought in Dec. 500 rounds with no issues. Then started having issues with dead trigger (click no bang) Was primarily happening in colder weather/ outdoors I attempted to address issue on my own with cleaning lubricating, etc. seemed to fix but then failed again. Sent into Sig. 1-day service, btw. Armorer’s notes are attached. Reads like they mostly cleaned and tested the weapon. Today the first 100 rounds fired flawlessly, then issue returned. I cycled the MPX repeatedly and normal operation returned. I’m not sure if there is a cold weather issue - or something else going on. I fully stripped, cleaned, and lubed (Slip 2000) BCG after session and action feels smooth. Any advice thoughts welcome.

Thanks