Hi!
You can go to the mpnp office and tell the receptionist about your situation definitely. They prefer you to have the same job from the beginning of your employment here in MB, but they still let you change your job at any point. There has to be a good reason, too.
In my case, Somehow, they considered being fired was not my fault, so they gave me 2nd chance. Then, between I was nominated and I applied for PR, I changed job again simply because I was not getting full time hours that my new employer promised me and I did not want to rush to have that employer ruining my life financially and Visa wise. So, I got another job after. After 3 months, I was fired again.
So every time it happened , I thought it would be the end of my opportunity to get a PR, but our mpnp officers are quite understanding and compassionate. So, you can trust them
Good luck!
MPNP Nominated: Nov. 2016
Passport Request: June 2018