When you deal DMG that amounts to roughly 30 000? points or more (+/- 3000) your score is detracted from the overall result.

It's easy to replicate with +X% score perk but as it turns out, you can still get this bug even without the perk should you deal DMG that amount to 30 000~ points.

Edit (an example of this happening):

The chain is active
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2591701270
The chain is finished [negative scoring]
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2591701584

The chain is active
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2591835315

The chain is finished [works like it should]
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2591835527

The chain is active
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2591835798

The chain is finished [negative scoring]
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2591835993

P.S I don't know anymore, I've been observing this bug occur here and there and there is almost no pattern to it except for the fact that your DMG has to be relatively high 2000 or greater.