Ram preview slow with new track matte feature

Using a Mac Pro (older) with a  3.5 GHz 6-Core Intel Xeon E5 processor, 64 GB ram, and an 

AMD FirePro D700 6 GB.  Never any issues until now.  Just set a couple of simple track mattes in AE 23.2.1 and it won't run a ram preview.  I opened an older version of AE with the older track matting feature and it runs perfectly.  Anyone else have this issue?  Thoughts?  Ideas.  Many thanks.