Bubbles under the PEI surface will happen with time. If your Lulzbot is within the warranty window, contact support and they will send you a new heater, glass plate, and PEI surface assembly ready to install no questions asked. I should know, they replaced mine 3 times. Great support!
If you are outside of warranty, Lulzbot sells PEI sheet replacements. The replacement instructions are in the last post.
You can prolong your PEI sheet and reduce bubbles by making sure you remove parts, like ABS, at their recommended removal temp, in this case 50C, and being careful not to let the bed cool completely before removing it or heating the bed back up to remove it. Best practice is to remove it right when the bed hits its recommended removal temp.
Adding a bed temp hold also helps if you can’t be right by the printer when it finishes.