this has been driving me insane for like two weeks. running a rush tank solo on a 5inch build, bound to my radio fine, goggles are picking it up but every few minutes of flight the image just tanks and i can see in my osd that the vtx has dropped to 25mw from 400. it comes back after like 10-15 seconds sometimes but sometimes it just stays low and i have to land and power cycle everything

i initially thought it was a heat issue since the vtx is kind of tucked in tight but i added some airflow and it didnt change anything. temperature readout in the osd doesnt look crazy high either. tried different channels, tried different power levels as the default, nothing consistent

running betaflight 4.4 if that matters, fc is a mamba f405. ive reflashed the vtx firmware once already

check your pit mode wiring and whether pit mode is getting accidentally triggered. the rush tank solo has a pit mode pad and if thats floating or picking up noise from somewhere it can pull the vtx down to pit power which behaves exactly like what you're describing. had this exact thing happen on a build last year and i spent forever thinking it was thermals.

also worth checking your fc uart assignment, sometimes if theres a conflict with another peripheral sharing that uart you can get weird commands getting sent to the vtx. in betaflight go through your port assignments and make sure nothing else is on the same uart as your vtx

could also just be a dodgy vtx tbh. i had two rush tank units in a row that had intermittent issues like this and both ended up being hardware, no amount of firmware or wiring fixes helped. the rush stuff has gotten better but their QC is still kinda hit or miss depending on the batch. if you've tried the obvious stuff and it keeps happening might just be worth swapping it out and testing with a different vtx before you go too deep down the troubleshooting rabbit hole