tempo is incorrect at times

Thanks for your help.
I may have found another better workaround, which may indicate the bug’s cause.
My MuseScore2 Tempo Change sometimes plays at the wrong tempo in 2 ways:
1. One edit step behind, after a tempo edit, illustrated as follows, and
2. It changes playback tempo when no (visible or invisible) change is present. (It may have been an old Tempo Change that I deleted). I cannot illustrate this but I resolved it using the following procedure.

Procedure:

1. The following Tempo Errors.png started with no tempo changes in view.
2. For the creation of Tempo Errors.png, first I inserted 140bpm at bar #1. Bar #1> played at 80bpm (default insert) instead of 140bpm, until playing the next Tempo Change correctly (not in view).
3. Next I inserted 130bpm at bar #2. Bar 1 now played correctly at 140 ! But bar 2> played at 80.
4. I then inserted 120bpm at bar #3. Bar 1 played at 140. Bar 2 played at 130. Bar 3> played at 80bpm.

5. At this point I captured Tempo Errors.png:
   
   The Play Panel confirms bar 3 beat 1 playing slowly at only 80bpm just 4 seconds into the piece whilst Inspector shows Follow Tempo Text of 120.0 bpm, the tempo I set.
   Auto save does not rectify this error.
   But I found the following sometimes works. Based upon the above experience, immediately after the latest (flawed) tempo change, insert (Alt+T= any number) at the next bar or maybe note (= bar #4 in my png). Come out of it (Esc x2). Then select it again and delete it.
   This additional edit forces MuseScore2 to play the piece correctly timed for all my tempo changes, which saves losing all my undoos or exporting flawed practice Flacs.

6. Finally, I edited/changed bar #1 from 140 to 120. Bar 1 still played at 140. Bar 2 at 130, and so on, one tempo edit in arrears.

7. I selected bar 1 beat 2 stave 8 (not in view) and Alt +T = 80 (default) & Esc x 2. Then I selected it again and deleted it. The piece then played as penned.
8. After another tempo edit that played erroneously, I tried insert (Alt+T= any number), followed by Undo instead of Delete. That too worked and rectified playback.
9. What does not work is Undo (120) followed by Redo, or add notes.

10. The next day, the file would not load—see Load Error2.png. Ignore and rectification twice, resolved the bar 18 issue, but none of the above worked!

11. The first successful repair of my tempo change was to Save, Quit and reload MuseScore2 (the third time).

12. The second successful repair of my Tempo Change was to use the Tempo Change Plugin. Set both start and end to your desired bpm.
    Anyone who can link experience with cause and fix this bug, I will applaud!
    So the two reliable functions are the default 80 bpm and the automated Tempo Change Plugin!
    What does the automated Tempo Change Plugin do that I do not do?

871c8ce on Windows XP SP3 on HP Laptop

#78416: Tempo text oddities in score with linked parts until save/reopen Seems to only affect parts, where this and https://musescore.org/en/node/100046 seem to affect the main score only. They may be related since parts are involved in both, but this one is seen in the main score while #78416: Tempo text oddities in score with linked parts until save/reopen is seen in the parts.

Seeing the score (.mscz file) can give insight that a picture of the score does not.