Hi DEV!
About minerpool.online:
in settings of the pool periodically in the section "payments" there are unsuccessful (failed) payments, I transfer them to balance - "Add to balance", but they are not paid and probably at the next failure again appear in the section "failed" with the cumulative result (accumulate). Most likely they are the reason for the different rewards.

The rest of the payments are normal, but some part of the pool can not pay automatically, tried manually, also failed to pass the payment.
What should be done on the pool?

DELETE EARNINGS  ?
CLEAR EARNINGS  ?
UPDATE BLOCKS  ?