Need help on walk in frezzer

I'm working on a walk in freezer. I found unit low on ***** mp66. did not have mp66 so I used hot shot 2. pulled a vacuum down to 500 microns. started charging unit. about 30 mins later my compressor went off on external overload. I cooled compressor down with ice. found mars relay 64 burnt contacts. replaced relay and also installed a hard start cap. after compressor cooled down it started. again after about 1hr or so it went off on over load .I tried adjusting expansion valve to lower super heat. super heat was high. also there is a hold back valve on suction line. I I did not change liquid line filter. could there be a slight restriction in dryer causing super heat to be high. Im going back tomorrow to change filter dryer and start all over. can any one give me some advise

Not very experienced with refrigeration work but, is hot shot 2 some kind of drop in for mp66? If so, is it a direct drop in or do you need to make modifications? Is it also compatible with that compressor?

For the liquid line drier, check the temperature drop across the filter drier and that will tell you whether it's restricted.

Next time you're out there, take a note of superheat, subcool, compressor amp draw, supply/return air and pressures and let us know what you find.

Are you an engineer was there a leak did you fix it !