What's this and what's it doing inside the fl3 printer?

I was replacing a Resin Tank and happened to look inside the printer. Inside was this. It is one of four corner cushions inside the tank box that must have stuck to the tank and then landed inside the printer. Once the tank is installed you cant see inside.

it’s black and was doing a good job of hiding inside the all black interior.

Yes, those things are a PAIN.
When I got my first Form 3, and when inserting my very first tank, I accidentally left one of those inside in the back left (when facing the printer) of the printer. The LPU crashed into it which then crashed against the limit sensor for the LPU which made lots of awful noises and the printer obviously refused to go anywhere.

I did manage to find it out (which was hard to see a black thing inside a dark place) and noticed the limit sensor was bent from all the pushing and hitting. I bent it back and it has been working flawlessly ever since.

Even after dozens of new tanks, I still check if all 4 foam corners are inside the box or not before inserting the tank. Learn by mistake, that’s life.

Those things should be banned and replaced by something with a fluorescent yellow color and stuck to the box with the hardest glue available!!!

I agree with you guys they are WAY too easy to miss. I got lucky a couple times when the remaining one(s) fell off before the tank made it into my printer. Bright would be great, or at least they should put some labeling or something on the front of the tank reminding you to remove them.

i was having issues, odd noises and bad prints I guess this may have contributed to the cause.