An exercise with 50+ phrases/sentences is too much
Some of the verb tense exercises become a marathon of frustration.
I've had at least 60 sentence long exercises in Hungarian recently because I just couldn't get the sentences right so I had to try again and again. My solution was to focus on getting just one or two sentences right so that the number of repeated sentences would diminish eventually. I'd just enter one letter for all the other sentences and wait for my target sentence to come again so that I could try again.
Do you feel like you are getting a lot of exercises per lesson? If you get a problem wrong, Duolingo will consistently (and in some cases, annoyingly) persist with the same problem until you get it correct. If you try to focus maybe you can get more correct and shorten the lessons. The lessons should be at maximum five minutes - they're supposed to be short little things.
On another note, though, I've heard that this could be a glitch.
Yes, I agree. I prefer the way memrise's reviews work. You know their length before you start and they are short enough so that they can be performed even when you only have a couple of minutes to spare.
Edit: Another good thing about a memrise review is that you can abort and your progress will still be reported.
I write down the most difficult sentences in an exercise book. I prepare colourful bookmarks for each new lesson. https://zapodaj.net/809c8b92ad056.jpg.html I cannot image how I would cope with the French course without it, especially with listening excercises. Probably I would have to make 60 sentences like Chirelchirel. Usually I need my excercise book for a few first repetition sessions. Later I do not need it anymore and even try do start practising with timer. Sometimes I take the book with me and practise offline :)