ERROR: Table is Mutating, Trigger or Function cannot see it.

On pressing both the highlighted (yellow) save button, insertion in table ANL_OI_DEFEKT is happening. (With Insert Statements).
On pressing below save buttons (checked with red pen), one procedure is getting called which merge the records (insert if it already doesn’t exist otherwise update the record) in table ANL_OI_DEFEKT.
Now in database, I have created a before insert trigger (ANL_OI_DEFEKT_TRIG) which is populating a col in table ANL_OI_DEFEKT with a DB sequence based on some conditions.
Above yellow highlighted save buttons working fine, but below Red checked saved buttons throwing below error:

How should i handle this?
Regards
Dimpy