Kehaulani's reply has given me an idea. Since I have never had a problem when playing our 90 minute band practice non stop before the Covid change, tomorrow, during the 20 minute break I am going to my car, sit in the back seat and play a series of easy exercises for about 15 minutes, taking rests between each exercise. Then we'll see what happens when we resume playing for the last 40 minutes of practice.
I'll let you know how it goes.