Sequence Type: servoy seq on MySQL VARCHAR(10)

Hello,

Have a MySQL DB where PK column is VARCHAR.
From now on, politics is that PK should be filled with auto-generated numerical value. MySQL auto-increment can be assigned only to INTEGER column type, I can’t change it because of the old varchar records.

Tweaking servoy seq and it looks usable for now, but some issues appeared already:
-how to configure Next value properly? When change the value in column’s Auto Enter tab and save -it jumps back to 1430. Value 1430 appeared randomly on 1st occurrence). Display of 1430 doesn’t change after new records insert neither, but it generates next values properly. Should Next value for servoy seq be configured elsewhere?
-how reliable is the usage of servoy seq+VARCHAR? Any experiences?

Or to implement custom logic on table events (onRecordInsert)?

Regards