betmgm slot paid line win but didnt add the bonus trigger amount

noticed something off while spinning last night. hit a decent line win on this egyptian themed slot and at the same time, the bonus scatter triggered. line win paid out, but the bonus trigger win that should stack on top didn't get added to the total. i double-checked my balance and there was no sign it ever got credited, just straight into the bonus spins with only the regular line win showing.

wasn't even a big stake, but it's the principle. i always assume the payout display is off somewhere, but this is the first time i've seen the bonus part not add up. anyone else run into this? do these slots glitch on split events like this often or am i missing something standard here?