Application crashes and not working without app pool recycle.

Question

Hello Team,
We have one application which sometimes crashes and throw 500 and 503 error code. We checked the status of application pool and found that the pool status always started and running but we saw that the database transaction was still going on, and it is impacting only on the UI part. In mean time we tried many solutions to resolve this problem but unfortunately it is not solving our issue.

Kindly help us to understand & locate this issue please.