I have this problem for some time now.
If something is wrong i press the reset button.
And i suppose its normal to Mach3 to loose the spindle position.
But what i noticed is somehow my workoffset becomes something else.
X,y and z are all gone.
this only applies to active work offset. Other offsets work fine after i home the machine again.

Does anyone experienced a similar issue?
And is there a way to make work offsets unchangeable?
Maybe a script to make a backup to a file for recovery.

Because when they are gone, they are gone forever 

You can set your Fixture position in to offset G59.253 and set the option in general config, this will then copy the figures into G54 on start up of mach3.

Are you saving your fixture offsets after you have set them from the offset tab.

Yes i know that. My problem is active work offsets change when i press reset. So if active offset is G58, it becomes useless, but npthing happens to 54,55,56,57 so on.

What is in the fixture offset table before and after this happens?

Why are you using so many fixture offsets?

Can you post your gcode.