I would not recommend moving forward with an alternate vendor before reviewing evidence of an independent review. A BSA/AML transaction monitoring vendor is likely going to be high-risk, in addition to critical because of the regulatory compliance implications. And critical and high-risk vendors should really undergo the highest level of due diligence before you sign the contract. If you moved forward with that vendor without validation, consider the time and resources you may need to invest to remediate any compliance issues that were found.
So before you switch to an alternate vendor, I would recommend obtaining that independent review to ensure you aren't dealing with larger issues down the line.
I hope this helps and I'd love to hear from others who have been in similar situations.