What was your money like when it broke for you, and what room/s did you fight in? 

When hoarding large sums of coins (+100k/+500k/+1mil) on the day market re-stocks, enemy level skyrockets (up to the 1000s when you have 1mil+). Seemed to me that a big level gap between invader & defender breaks combat somehow, though not with regard to the to-hit chances, but damage. Seems there's a level multiplier in play in the background; and with that at work, when you pit a lvl ~1000 invader vs a lvl 50 defender, defender attacks will deal about 0-2 points dmg, while the invader dude can basically one-shot you with a jab.

I did notice that such high-level invaders will also play all their combat anims in one go & REAL fast, only so far it didn't break my game like it did yours. May also be that itz putting too much load on your rig in that situation, thus freezing & breaking combat - this game hogs more RAM/VRAM than CP2077 on all ultra, judging by the speed of my RTXs cooler fan^^. 

And there was one other thread that discussed combat being broken/bugged, but only in certain rooms, though much like you described I think: Freezing OR not being able to target invader, thus unable to win without gadgets. So maybe change the room interior on your defender's spot, see if that helps any. And avoid hoarding loads of coin on re-stock day, take note of invader lvl, if big lvl gap is the issue maybe. No other ideas on this topic, sry.

It's true the gameplay loop starts to break down at around this stage due to gold hoarding and how the power scaling doesn't account for the fact that you can just run several gold mines at once, or maybe it does and you're just expected to have hoards of followers die per invader.
Since I started with the idea of just creating a spike corridor, I figured out quickly that any invader will die or come close to dying before they even encounter anyone. (You might want to consider starting another save to try this)

For whatever reason, all the status bars, in this version, are fixed at 100, and 4 level 5 spike traps do a fixed 26 damage (you do the math on that one). With a graveyard and an alter, you have the option to revive any of them and now you have a high levelled zombie.

If you would rather have high levelled living followers or don't want to put in a spike trap corridor, then:

• Use Nail Bombs! Nail Bombs have the equally amazing property of having fixed damage, just chucking 7 Nail Bombs at someone(7 x 15 = 105 damage) will always take them down to 0 health. Unlike in monster capture games, a character at 0 health only dies once you end your turn, which means you can either use the capture ability or Shackles.

• Send followers out to capture others. Whether you managed to capture a high levelled follower, or they somehow died, you can always send them back out in search for others to bring back (yes I mean sending zombies out, not just a corpse). Followers will always capture others around their level.

This all being said, high levels become a bit pointless since combat just turns into sticking sharp objects into anyone until they either submit or die, but it at least gives you the freedom of keeping whoever you want despite their combat ability.