Jump's Fluid protocol has a feature where it will try to temporarily change the display resolution of the remote computer to match the screen you're connecting from. If you want to disable this feature, try this:
On Windows & Mac: Right click your connection icon in Jump and then click Edit. In Display section makes sure Resolution is set to Same as remote computer.
On iOS: Tap the "i" button next to your computer's name and then tap Edit. In the Display section make sure Change Resolution is disabled.