Ghost spot on a 2445 sreen


This topic again about a strange thing on the screen of a 2445.
A ghost, not focused spot flashes randomly at a stable location on the screen, whatever the brightness setup, vertical scaling, tme base, triggering, etc...
When the scope is turned off, this spot remains visible during about one minute, before disapearing. A possible source could be a default regarding not enough screening from high voltage area, or a leakage problem, considering discharging capacitor time as an information to investigate the root cause of this ghost spot near the middle of the screen.
Waiting for any help or advice, if any idea or known problem.
Thanks and regards.