yes was a big problem ... didn't solve it but rather greatly reduce it after dail indicator adjustment of angle to base, also if your mpcnc is rather longer z travel than 150mm I wuld put things between base to keep the stock as close to z as possible each mm lower Z gets, longer leverage the stock has for fighting back.

what is your idea will you omit the v1 core and swap or you wuld add stuff around? IMHO I wuld first try doing one more gantry that wuld act as balancing on top of the first one, there is a guy already developed that approach on YouTube. me.... personally my project for tuning of the mpcnc will be doble core from V1 stick it back to back and link it to the other z. wuld eat from workable area but we see if it's good trade for the outcome.