The newest update, 1.2.3, adds a cool extra trick from Freakager to remount Ragno when dismounted. However, this sometimes causes Ragno to break entirely, and I'm not really sure why. I think it has to do with Ragno being in the middle of other behavior and thus being unable to start digging, and rather than waiting until it's able to dig, it enters an errored state where it stops attacking and becomes completely invulnerable (even to Creative attacks).

Here's some extra context, if that helps diagnose the issue.
I'm attempting to give the Freakager some extra behavior via datapack for a modpack I'm working on. One of the changes is that he wields the Warped Axe from Dungeons Plus instead of his typical iron axe. The Warped Axe's gimmick is that it teleports the user when it lands a ranged hit, so I've mimicked that behavior via commands to forcibly dismount Freakager and teleport him to the player when he successfully lands an axe toss (with the intent that he'd then follow-up with some kind of point-blank attack before remounting Ragno). Most of the time, this works beautifully. Sometimes, it doesn't. This may or may not be caused by Freakager dismounting during one of Ragno's attacks. Freakager will drink his potion, but Ragno will simply lock in place. When Freakager reappears on top of Ragno, Ragno can move again, but it refuses to attack or take damage. Freakager functions normally and seems entirely unaware that his pet spider has gotten a surprise lobotomy. Killing Freakager lets Ragno function normally again, but other than that, I can't find a way to fix it on my end.

To test this, try running /ride @e[type=illageandspillage:freakager,limit=1,sort=nearest] dismount periodically during a fight, particularly when either or both of the bosses are mid-attack, including Ragno's leap. It should happen eventually. If you can't reproduce it, I'll try and narrow down the cause more and come back with a more specific report.

I recognize that messing with commands like this can cause tons of edge case bugs that are impractical for a dev to fix. But in this case, this seems like it might be able to happen even without someone like me messing with the boss's behavior if Freakager ever gets dismounted at a bad time (example, if Ragno leaps through a waterfall or something).

Hmm...

particularly when either or both of the bosses are mid-attack, including Ragno's leap

Ragno shouldn't be able to leap in phase 1 though. Otherwise what's supposed to happen is when freakager takes out the potion it should cancel whatever attack Ragno was in the middle of, so not sure why this would happen...
I'll look into it though

Ohhh, wait, I think I found the issue. Will be fixed!

Thank you very much! This will help immensely. Great work on this update, by the way; all of the little tweaks in 1.2.3 make the fight even more enjoyable.

Fixed in latest version

Thanks and glad you enjoy it :)