Zend certified PHP/Magento developer

Class BuyRequestBuilder does not exist after upgrade 2.3.5 to 2.3.7

working on an upgrade from 2.3.5 to 2.3.7 and suddenly got this error when compiling, does anybody know how to fix this?

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Looks like it had to do with me changing to “minimum-stability”: “dev”, because of mageplaza smtp asking for that.

I tried to search for information, did a complete new composer install but still the same error.