Metric modulation markings don't respect previous tempo

Describe the bug
Metric modulations (like quarter = dotted quarter) do not affect playback when added to a score, but take effect after toggling "Follow written tempo" off and back on

BK Edit (note to developers): metric modulation markings seem to reset the tempo to 120bpm, rather than respecting the written tempo. This is why toggling "Follow written tempo" on and off works to achieve the expected metric modulation. Ideally, when adding metric modulations, they should automatically follow the written tempo.

To Reproduce
Steps to reproduce the behavior:

1. Fill a score with eighths
2. Change from 4/4 to 6/8
3. Add quarter = dotted quarter from Tempo palette
4. Play
5. Hear error: eighths stay constant

Expected behavior
The eighths should get quicker so the beat stays constant (quarter in 4/4 same tempo as dotted quarter in 6/8)

Platform information

• OS: Linux

Additional context
It is fixed up toggling the "Follow written tempo" off and on. It remains fixed even if you change the original tempo - the metric modulation does correctly adjust to the new tempo. So it's only off when first added.