Not a verteran lever user, but happy to offer some comments.
First question, cleaning of the machine immediately after use will generally give the best life and least amount of problems.* As a bonus, if something is going bad you will find it much sooner.*
Second, sorry dont know much about the specific issue you asked about, hopefully someone else with one of these untis can help you.
Third, around here we often use phrases like... "Its whats in the cup that counts", so if you thought the brew tasted good, dont worry too much about the condition of the puck.*You might try some variations in your dosing process, and see what it tastes like. Lever machines enable some big variations of brewing parameters, which might make some other parameters vary more, compared to pump machines for example, however other things you observe as you continue your journey can all help in the long run.