Something similar happened to me, do you remember if you were in a restricted area like ms area or something? If the area got removed maybe you're getting crashes for that reason. I'm sure it will be resolved soon :D
Hi! Sorry for bumping the topic again :/ I think I have the same problem.
After I got ported in Kanto I played in this region for a couple of days: I could use surf and dig to travel with no problem, I went from Viridian to Fuchsia, then back, then to Cinnabar and the lab and mansion with no problem. I could also access the safari zone with no problem. Basically everything in this region was fine. I didn't try going to Johto but I guess it'd be fine since I'd have to go on foot/bike. I didn't try going to Love Island by ship and I haven't unlocked other places if I'm not mistaken.
Then the crash happened when I went from Vermillion to Lilycove by ship. I arrived at the house with the sailor and when I exited the house the game crashed. Then I restarted and it crashed again like the other times. So I think it's related to the previous crashes because I originally had gone to Vulcan from Lilycove. Also when @Shamac tried to help he ported me in Lilycove poke center after Vulcan, and as soon as I exited the poke center the game crashed the same way. So I'm thinking that when I try to return to Lilycove like I did after leaving Vulcan Island belatedly the game crashes for me. I tested playing in Red server just to make sure, and the game doesn't crash there so I think that the client etc have no problems.