First I have to say that I am very impressed with this new function! It was a long waited option to ride on bicycle within the previously recorded random (or borrowed other) track with the voice prompts.
So after some testing with random tracks I have two rationalization suggestions.
Thank you for your detailled review, suggestions are always welcome.
1. I think its a good idea to voice the distance to the next driving maneuver provided that the distance to it is more than 1 kilometer. I have to explain this. When riding with the phone in the pocket, after the another turn you dont know how many kilometers you have to go further. So for example riding half an hour with silence you mentally start to worry about the program itself (it may crash) or phone itself or any other shit can happen! BUT when you know exactly that you must ride forward for 5,5 kilometers you can just relax and pedaling. ))) Just say "Keep moving more than 5 kilometers".
So your suggestion is to add an additional instruction in case there is a long distance to the next turn. Fully agreed.
In case you get off track the off-track notification should help you but you are right, empty battery, crashed phone, pulled off plug from the phone, etc. are things which may worry the user. We should keep in mind that there shouldn't be awful lot of TTS hints because this becomes annoying after some time. But just one more after the last turn before a long straight part of the track should be ok. I'm not sure when the first announcement for the next turn comes but the new one should only be inserted in case the distance is much longer than the distance for the first announcement
2. Recorded tracks often have the errors or unnecessary movements on the spot.

I think it would be a good thing for the algorithm to ignore the small track inaccuracy within 20-30 meters. I.E. if the radius of the some maneuvers is within the range of 20-30 meters and after them the direction of the route is still the same - there is no need to specify maneuvers.

The voice guiding will be confusing in such case.
Or in general if the track has more than one maneuver (change of the directions) within the range of 20-30 meters it would be logical to only take into account the last waypoint where the direction is changing.
For example in this case we have not the true left turn but "take the left" only.

What setting did you choose for your navigation? I guess "Number of orders = High". Try with Medium (you can do it from the sofa, no need to do the >100km ride again) for the critical situations.
Maybe I should explain what this "Number of orders" actually means. The setting is not to let the TTS talk and talk and talk. The idea is to configure (and my proposal for this setting is still "minimum expected distance between turns". "Number of orders = High" is I think equivalent to "Minimum expected distance between turns = 20m". I don't know the equivalent for medium and low, Menion should tell us.
I could imagine that 40m or 50m would be ideal in your case. Keep in mind that the algorithm for "Navigation on all tracks" is without any knowledge of roads, it only knows the track and it doesn't know why there is a turn in the track.
Why is high equivalent to 20m nevertheless useful? People also use accurate tracks, e.g. calculated by brouter (c.f.
http://forum.locusmap.eu/index.php?topic=3434 for details) and if you e.g. take a ride through a village not following the main road it happens quite often that there is a sequence of two turns like a zig-zag with a distance of e.g. 15-40m. The setting medium as well as your proposal will not detect this zig-zag.