There is a long standing... quirk where if a shot with passthrough gets reflected, such as Katana star cannon "reflected" off of a Dwarg Behemoth, more shots are cloned and scattered. I guess this is caused by reflection not actually reflecting but creating a new shot and sending it to a new direction. If the original shot survives due to passthrough, it, along with the copies, can continue and hit the target again, for more shots.

The problem with this quirk is if a shot has passthrough close to 100 and tracking, it can cause a (near-infinite) loop that can slow the game to a crawl.

A suggestion to prevent this is if a shot gets reflected, treat passthrough as zero instead of its original value and do not let that shot survive.

george moromisato 12 Dec 2019:

Fixed in 1.9 Alpha 4. Reflected shots do not pass through.