Structural member: part deforms when changing frame

Hello,

I want to delete a square tube from my frame. When I do this, the whole frame deforms and tubes are repositioning themself.

Is there a way to add changes in the later stage of modeling without having to worry about deforming?

Here is the tube I want to change.

I deselect the sketch line from the structural member.

As you can see, some of the other tubes also disappeared and some changed position.

Anyone knows a solution to prevent this?

Or any tips for building up the part to prevent this in the future?

I am new to Solidworks so tips and critism is also welcome so I can make myself better.

Kind regards,

Bjarne

SolidworksModeling And Assemblies