If a character capable of counterattacking gets attacked multiple times, they can get locked into counters, doing nothing but counterattacking for several turns in a row.
Not this.

Pressing 5 once (note the time):

Logs (note that "Saving game" was 10 seconds ago):

Additional thoughts: even the way it is intended to work, wasting moves on a counter may be undesirable, e.g. if the survivor is escaping a horde of zombies, he doesn't want to waste any amount of movies attacking them. Maybe a better way to handle counters would be to mark/highlight the zombies that make attacks that open them for counters, and make counters performable by attacking marked zombies.
Can confirm. I spent 4 minutes roundhouse kicking ants at a military outpost after walking up some stairs. It seems like a high encumbrance is part of the cause. With 100 torso encumbrance and 20 on other bodyparts it takes 30 seconds if a giant ant attacks you compared to the 1 second at low encumbrance.
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Additional thoughts: even the way it is intended to work, wasting moves on a counter may be undesirable, e.g. if the survivor is escaping a horde of zombies, he doesn't want to waste any amount of movies attacking them. Maybe a better way to handle counters would be to mark/highlight the zombies that make attacks that open them for counters, and make counters performable by attacking marked zombies.