I thought it was just me!
I have now an Ender 3 Pro and an Ender 3 pro v2 and both get severe under extrusion while in the Creality enclosure.
I live in Iowa, so, I got my enclosure around January and the printer (one at the time) was fine in the enclosure.
A couple of months ago when the weather started to warm up, I noticed my prints would be fine for about a half hour --then issues!
It's not just you!
Kinda defeats the purpose of fire safe, if you have to have the door, or vents open. I just tossed the enclosure in the other room.