We used to use our current vendor for about 15 years when we were first getting started with this business so it was familiar territory but also very much not what I enjoy working or would recommend others do as well! The customer service side of things can be lacking at times which makes managing contracts difficult sometimes too - especially if you have multiple vendors onboarding clients all over time zone boundaries/countries (which happens frequently).
Our previous provider did nothing wrong per se just that they didn't really understand how important their work ethic could affect other aspects like client retention rate etc., while ours has been quite good overall since switching over from them 2-3 months ago now :).