city connection bug?

[miaasma]

i'm playing austria with 11 cities, all connected by roads. at around 215 turns, all of my city connections randomly break. no pillaged tiles, no AI or city state borders interrupting, and it happens to every city regardless of location relative to the capital. they're all land locked cities, so no harbour-related issues. is there a solution or explanation to this? has anyone else experienced it? i'd like to be able to continue this game, it'd be a shame if a bug made me have to restart

 

[miaasma]

update: saving, exiting the game, then opening it again and reloading causes the city connections to return, and the resulting GPT will be restored on your next turn. still interested to see if anyone else has seen this