MM on several devices

[Weirdscenes]

First off I must mention that as a 75 year old music fan I liked MM a lot.
First I need to excuse my crappy short term memory and say I often can't recall what some onscreen messages have said.

In recent times - probably since the last couple of updates - I've been having very frequent and lengthy hassles where I'm unable to use mm.Thats because, on my main music source (an Elephone Soldier containing a 512 GB microSD card, on which is a copy of all my music - around 250,000 cleaned up music tracks) is endlessly scanning/updating etc.
I use 3 different android devices on which MM is installed, but mainly the Elefone. The other source I use frequently is a Ulefone Power Armor 13 -bso far I'm having no issues with that. Although I have MM installed on an 8" tablet, I rarely use that.
(I also have a couple of PC's which I rarely use & don't have MM installed - maybe I should ?)

As I write this I'm realizing that, although I mainly use MM on my Elefone, possibly my issues are complicated by the fact that each device is stand-alone and not synchronized.
So far, when I play music on my Ulefone Power armor 13 via MM, I'm not having any issues presently - even after running "Duplicate Files Fixer"

I don't understand the synch function at all so have barely looked at it.
I'm guessing that it's likely my problems are occuring because my various devices aren't synchronized ?
Once again I must mention that I'm an old man now & although I was once very adept technically, I'm now a bit of a plodder and get confused at times.

I'm also finding it quite difficult to submit bug reports etc because I mostly use my phone which actually has a small keyboard and screen, and I have fairly large fingers - it's easy to make mistakes.

Finally I should also mention that I play my music, mostly outdoors on my balcony, by connecting via Bluetooth, to a small amp, wired to a pair of speakers.

I've uninstalled and reinstalled MM several times on the Elefone - to no avail.
It's probably worth mentioning that recently, possibly concurrent with these issues, I've been making attempts to edit incorrect titles and to remove duplicates. As previously mentioned, for the duplicate removal I've used "Duplicate Files Fixer".

I also would like to know just how long a scan should take, I have around 250,000 songs in my dedicated music folder. (On the Elefone)
Please help

[Lowlander]

Are you moving the SD card between the different devices?