Anomalous Tempo marking behaviour in some files

This is a bit strange. I have some files created in MuseScore 2.3.2 with a Tempo marking the first beat - it's actually a rest but that appears to be irrelevant so far.

Sometimes the Tempo marking doesn't match the Play Panel BPM when it is playing. In fact, the Play Panel (and playback speed) is always one change behind. See screenshot:

Example:
1) Open file. OK. Plays at correct speed. Play panel displays correct tempo.
2) Edit tempo marking to, say 300 BPM, rewind, play. - Error, file plays at original speed and BPM shows original speed.
3) Edit temp to 50 BPM, rewind, play. Music plays at 300 BPM and Play panel displays 300 BPM.

This happens in v2.3.2 under 64-bit Windows 10 on some files. I created new file and that file seemed to work OK.

I also tried opening a copy of the file (which works incorrectly in v2.3.2) in the latest nightly build (MuseScoreNightly-2018-08-11-0348-master-9ccae66.7z) and it worked OK.

It looks like the tempo marking is attached to something slightly before the beginning of the score and is ignored on rewind. Subsequent tempo markings are interpreted correctly.

The tempo marking seems to be attaching to something before the point at which the search finds but the search seems to find the previous tempo. Almost as if it's looking in the previous edit history! I hope that makes sense!? I have attached a copy of the file Moonlight_Serenade (Rusty Mscns) with tempo error.mscz .

The only way I can get the file to play at the correct speed is to edit it to 90 BPM, rewind & play. Then stop, edit it to 91 BPM, rewind and play. (but the text is now set to 91). Or save, close and reopen the file - that works.

Has anyone seen this before and know what I can do to fix it? I suppose I could create a one beat rest before the start of the score and attach a tempo to that but I'm hoping there's just a corrupted thing somewhere I can delete and recreate.

Oh, and I tried deleting the temp and creating a new one but that didn't help.

Thanks in advance.....