This problem is since at least 7.4, but I'm pretty sure it started before that. I'm using the latest official maps and have tried the 7.41 beta which didn't help at all.
I recently used some routes that I know worked previously, because I designed and used them. However, lately TBT is completely broken. When I ride the route the entire time it shows distance to destination as the full route length, and distance to next turn as 12 feet or so. It never pops up the map for TBT directions as it should, and I have to keep the map screen up to avoid mising turns. It does show little the popups for turns if there is a cue sheet, but they are so brief and don't happen far enough in advance. I need it to switch to the map screen and display the turn in 50m advance like it always has in the past.
I'm grateful for all that Garmin support has done for me lately, but OMG when are they going to stop with the crappy software quality. I'm really glad DC Rainmaker has called them out for it. It's time they join the rest of the industry in software best practices and provide reasonably stable products to their customers. Once again I find myself considering Wahoo. Many of my friends use it and are quite happy with it, claiming they never have issues.
