Hi,
Over the past couple of weeks I've noticed that whenever I open another app (e.g. WhatsApp) or when my phone screen turns off due to inactivity the Deezer app closes and I have to reopen the app from scratch. This never used to happen in the past. Whatever updates you have done please undo it as this is highly impractical and extremely annoying, so much so that if it cannot be fixed I'll have no choice but to find another music app. I have tried clearing cache and restarting my phone, it didn't fix the problem. I'm using an iPhone XR, fully updated with latest available software.