Indoor Rowing manually editing SPM (Cadence)

i have a rowing machine that I have to manually record my stats after the row.

I use a solar instinct to record the row ( heart rate, strokes & time)

Then I later edit the activity to put in info such as Distance , Power, and CADENCE (both Avg & Max),

However when i go back into the activity the Cadence value are wiped clean, it is like they are not being saved.

Anyone else experience this ?

Also is there any way to manually enter (5 minute) split stats post activity?