App issue on android

Hi, hello. I'm not sure how to accurately describe the issue I'm having, so bear with me!

On the last two longer runs I've done, 16k last weekend then 18k today, at some point I've noticed that the app hasn't been in my ear telling me to slow down or speed up in a while. When I've then gone to look at my phone, it's like the app has frozen and then jumped back into action when I've turned my phone screen on. It's then done a GPS 'jump' to catch up with me, and will tell me I'm XYZ distance through the run - I don't know how it is then assuming my distance. I can tell its not accurate as the map on strava then shows an 'as the crow flies' line, instead of the accurate line.

IF that makes sense... any suggestions?! I'm on Android and have already checked the battery optimisation settings are as they should be, which is all I can really find as a suggestion on Google.