Changing time in key creates measure of wrong length

I’ve changed time in key in a track from 3/4 to 4/4 (using “C” symbol but the same is with 4/4). After that, the first measure is in 3/4, wrong length, and the successive measure are of the correct length, 4/4. I’ve tried to delete and reinsert time in key but the result is the same (see screenshot).

I’m doing something wrong or Dorico 5 has a bug?

Thank you

there might be a hidden meter change at rehearsal letter C
If you select that bar-line and delete it, what happens?

Thank you k_b for your answer.

I’ve enabled all sort of elements viewable.

There is a meter change in the bar with letter “C”, the 49th bar, see image:

If I’ve understand how Dorico 5 works there would be the change meter notation in 48th bar.

I searched for the tool to insert the change meter in the bar before, the 48, but I can’t find it.
If I insert the 4/4 or C notation in 48th bar, the notation itself is inserted, but the meter of the 48th doesn’t change.

Have you some suggestion?

Thanks in advance

put the caret in meansure 48 and type SHIFT + B + 1 + q to add one quarter note beat to your incomplete measure.

Changing a time signature in the middle of a piece with a subsequent time signature does not alter the number of beats in a measure (as a safety precaution) unless one has already activated Insert mode.

Thank you Derrek for the solution!