Maybe check the Event List and look at the Control Changes and see if you see anything significant.

If you have a set volume to start, and at (for example) bar 13 you insert a dot at a lower volume, it does not immediately drop to the new volume, but instead fades from the initial volume to the new volume.
You may need to insert a second dot at the same volume as the first right before changing it to a lower volume so the volume remains the same until you want it to change.

Could this be what you are hearing?
It is the default behavior; you need to insert 2 dots for sudden volume adjustments.

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