Nozzle too high compared to home Z

[Pietrogramma]

Hello to all I have an Iprusa geeetech PRO B with GT2560 card that until some time ago worked very well.
For a few months now, however, I have problems with the Z axis, that is:
when I send in home the Z axis the carriage goes down to activate the end stop, then goes up a few millimeters, to go down to the zero point of the Z axis.
For some time now, however, if I send the Z axis in home the carriage go down until to close the end stop, then goes up a few millimeters and stops, without lowering back to the ZERO.
This means that when starts to print the nozzle is higher than the zero point of the Z axis and obviously the print is irreparably compromised (the first layer, in fact, does not stick to the glass as the nozzle is too high).
Does anyone have any suggestions to give me to solve this problem?
I think, however, that it is an electronic problem (I think that the card is broken).
Hello and thank you

[William]

Hi，You can connect the printer to your computer via USB.
Enter M119 through the manual control of Repetier Host.
To see the status of the limit switch.
Specific operations can refer to this:viewtopic.php?f=17&t=60927
I hope this can help you.

[Pietrogramma]

Thanks Wlliam, I changed the end stop and now the printer work fine.
I hope to have solve the problem with the new end stop.
Thanks and ciao

[William]