Cat 305C - Boom slowly going down when cold

Hi everybody!

I've recently purchased a Cat 305C CR 2008 with 4100 hours on it. Overall the excavator seems in pretty good shape and was correctly maintained.

I'm new to this nonetheless and I've noticed that after starting the excavator (only tested on cold temperature so far - like 30-40F), whenever I lift the bucket with the boom, it very slowly drops down. When the excavator has been running for a few minutes (2 to 4), this seems to go away entirely.

What could be wrong? Anything to...

Cat 305C - Boom slowly going down when cold

Cat 305C - Boom slowly going down when cold