It is extremely concerning.Any form of negative behavior,even just minor squeaking,is an indicator that a pair is just not getting along well enough.This is fairly common too,especially considering that it is not natural for hamsters to live in same sex pairs anyways!
It would be much better to just separate them into two good sized cages(between 80 cm x 50 cm and 100 cm x 50 cm) rather than assume they're fine together just because they haven't actually hurt each other yet.This behavior will still negatively impact the hamsters in question,so action must be taken for their welfare.
Make sure you've got a proper upright wheel for each cage once they're separated by the way,as flying saucers are not a replacement for an upright wheel.They don't allow for a natural running position,cause side arching,take up a ridiculous amount of space compared to a proper upright wheel,and are just an unnecessary toy
