I'm running the latest restoration patch 2.3.2 (I upgraded from 2.3.1 mid game thinking it was okay since it didn't affect anything) and unofficial patch 1.02.30 and I've encountered an issue when trying to challenge dragon's men to a fight of skill.

The issue is after I've entered the ring and prompted with 'FIGHT!', the opponent doesn't initiate the attack and we're just stuck in the ring even after I've attacked and killed him. Sometimes on a rare occasion if I get knocked down it might declare 'YOU WIN!' but it's a unreliable way to get past all the opponents.

If I challenge Dragon or Lo Pan directly the script works fine though.

I also noticed if I try a much earlier save, the script does work! So I've done something to affect some state of Chinatown. The only quests I've done in Chinatown is the Brotherhood of Steel (BoS) quest. Other than that I haven't explored any other area of San Francisco (SF) except Chinatown. But even if I load a save before doing/initiating the BoS quest I still encounter the issue.

With this in mind I thought I could replace the SFCHINA.SAV file from a earlier good save since I haven't done anything in SF, but overriding this file can remove my NPCs and Car's trunk. So I though I could do the following:
1. Moved all NPCs and my Car to the military base and left them there
2. Saved
3. Replaced SFCHINA.SAV from the appropriate save
4. Challenge Dragon's men
5. Return to get NPCs and Car...

But my Car's trunk is missing anyway! :\
Any thoughts on fixes or workarounds other than not challenging Dragon's men?

Surprisingly I managed to resolve the issue, but the workaround was more primitive than using a save editor.

After successfully challenging Dragon's men, simply replace SFCHINA.SAV again with the original one. This successfully puts the Car's trunk back on the map and the state of the world appears to be retained i.e. defeated Dragon's men, Lo Pan's followers in grief, character exp retained etc.

If you revert back to the original SFCHINA.SAV after defeating Lo Pan, then he will be alive again, in which case you can defeat him again for no additional exp. His followers are still in grief even if he is alive.

I did try using a Save editor and check through all the global variables (GVAR), including those that determine Car's location tile but setting it manually to a known location did not work, the Car simply vanished. Also I couldn't see any differences with the SF variables.

Hope this is helpful for someone else in the future. I found it at least a bit illuminating in terms of understanding how the save game system works in Fallout 2.

(Also seems you can't mark your own post as a solution to your own Q... :\ please let me know if I'm wrong here!)

I don't know if your problem was originally caused by this, but supposedly Restoration Project patch already includes the unofficial patch and the author has explicitly advised to not install the latter with RP. The unofficial patch is intended for those, who wish to play the original, unmodified game with additional bug fixes.

If I remember correctly installing both patches will cause issues as they both try to access and modify certain files that the rest of the patches rely on. try only using Restoration patch and see if you can replicate the problem.

Bingo.

Do not install both the RP and the unofficial patch. The latter is included in the former to begin with, and installing both is known to cause problems.

DamoclesAlpha and SirGray already answered, but it can't hurt to repeat it. People still make this mistake sometimes.