Issue after the first print of the day

[EagleSeven]

My first print of the day on a flashforge creator pro using Simplify 3D always comes out perfect, but every print after always shows gaps on the first layer and under extrusion throughout the print. It also prints differently than the first time (some new and different curves).
There was a time when this never used to happen but this problem started a few days ago.
I've tried letting the machine totally cool down to room temp after the first print before starting the next one, but when I print I still have the issue.
If I leave the machine off and get back to it again the next day, the first print comes out perfect and then I get botched subsequent prints.

Any ideas?
Thanks

Could be a Voltage Drop to stepper-motors.
Caused by the Power-supply or Mother-board problem.
(I would first try an different power-supply)
Make sure Fans are working at both PSU and Mobo.

Or it could be a stepper-motor overheating and failing.
I've read about that happening and causing problem like yours.
(touching motors, after about an hour of printing, will let you know if Too hot)
(I have fan on X & Y motors to prevent that)