"Insert Silence" adopts incorrect tempo.

OK, thanks, but first I need to understand the inconsistency of the Cubase elements version as I have just noted that the required functionality does actually seem to be present in another project.
Referring to the attachments:
Where the step change in tempo is defined by the square dots. To make the step abrupt the upper dot is dragged as far right as it will go.
In the original post’s case [different example with the same problem] both dots can be dragged to the same time (5.1.1.0 and 5.1.1.0) so the insert silence presumes the upper tempo.
tempo2.jpg
In an earlier project I can actually get the insert silence to adopt the expected tempo because the upper dot cannot be dragged to the same cursor point (72.4.4.119 vs 73.1.1.0)
tempo1.jpg
I cannot see where this dragging inconsistency comes from.
Does anyone know which bit of the project settings defines the ability to drag the upper dot to the exact time location as the lower?
Then I can set the settings to give me what I want.
Thank you