Yes, as mentioned we tested the current version 1.2.15 and saw this message playing `2 Player' & `Endless Mode' - but we noticed from your former comment that you fixed something similar - so maybe a special case (caused by e.g. reviving) still faulting - and yes, we get this "hit chain +100" message when the score got reset and we both died. This happens also in between (so maybe several times zeroed before the final count is achieved ... so we don't know how effective we really are ... but playing just for fun is not touched by that bug - it's only the statistics ... :) but we are mostly too busy to get a feeling about the conditions triggering the score to get zero.
Thanks for the comments about the weapons ... and yes the weapon balance has improved ... so the remark is not a criticism but only a wish to keep the flow in Coop non-stop mode. It is really something contemplative for me ... just reacting by instinct ... really refreshing ... ;)