Jenkins webhook stopped running


Hi All,

I am using Jenkins ver: 2.155 with all relevant plugins were upgraded to the latest.
I have webhook which is triggered on create\update pull request events which stopped working before 12 days a go.
I also put skip TLS on webhook to check if it is related, but it did not work also.
On bitbucket webhook send request history I can see three attempts for every event that done that fails with the following X-Squid-Error ERR_CONNECT_FAIL 110 (HTTP 503 Error)
Any idea?