I have faced the same issue and got fixed with the help of this article. Thanks Eric

Yeah, Aggressive Doze mode is experimental and should be treated as such. When I tried it, it went alright, but that’s not going to be the case for everyone. Good to know that you had that issue, so maybe someone else can avoid it!

Had major problems with my Samsung S6 using Greenify’s aggresive doze feature. I only noticed it with Endomondo, but it would shut down my bluetooth after only a few minutes into my run, and I’d lose heartrate monitor function. Yes, it was Greenify, as when I removed it, all went back to working normally. Not sure if…