I think you have two choices at this point.
1. Since ProSeries normally is bug infested at this point in time, you might want to wait for awhile before doing the conversions.
2. If you don't want to wait, you should call support.
and ex marks the spot where those rocks and anvils hit me.
I spent almost a day, still cannot convert data from Drake to Proseries. Even with the help of customer support. They still cannot figure it out when the file corrupts. I call Drake 's customer support as well, and they said the file is fine. Sad..
Obviously it depends on the complexity of the returns involved, but the last time I changed software I opened the converted prior year return for every client in the new software and compared it to what was actually computed and filed in the old software before doing any future returns in the new software (I hope that made sense). So, in your case, going from Drake 2018 > PS 2019, I would open every return in PS 2018 (including state returns) and compare it to what was filed with Drake in 2018. Then you have a clean start for converting PS 2018 to PS 2019 and much fewer headaches during tax season. After a few of them you get a feel for things that do not convert over well so you know where to start with the rest of the clients. The first week of December might be a little late to start on such a project but every second/minute/hour/day you spend now is time you don't have to spend Jan.-Apr. This is why most people are reluctant to change software (and rightfully so, there's a huge up-front cost in time and manpower to do the conversion correctly, and then a much higher risk that something will slip through the cracks in the middle of tax season and then you're stuck paying penalties with unhappy clients).