Software has unending problems

I have honestly had nothing but problems with this software (which I have used since January of this year). 2 or 3 times a day I get a complaint from a customer that a transaction that they made has not gone through, or they are not able to sign up, or they are not able to sign in. I had so many problems with my subscription option that I had to kill it and reimburse my customers nearly $3,000. Is this normal, or is it something to do with how my Wordpress site is set up?