Redsail x700 laser

Hi I have just got an redsail x700 laser from redsail in china didn't know how to set it up but found someone to line mirrors and lens up done test everything was ok but know it could run for 7 mins at speed of 20 power at 65 cut 4mm mdf temp not going above 17 then I switch it off go back to the machine 2 hours later ask it to do the same thing and it will not do it it has reduced power laser beam is not as bright will not cut at even 85 power and speed 6 but leave machine till the next day it does the same thing everything is lined up properly redsail saying I have made wrong adjustments I have not made any adjustments can someone please help
Kind Regards William