Hi Alan,
I had many spourious Manipulate instances after upgrading to 13.1 on windows 10 Pro and reported them to Wolfram.
The problem seems to be, that all data produced by manipulations are dynamically stored in the notebook interface kernel memory. Depending on the size of total memory the Jlinks reaction times are growing larger with ever growing backuped data. After some time of working happily with Graphics3D manipulation, the complete system disappears from the screen. EventViewer of windows shows an exception caused by the Mathematica kernel.
After expanding the virtual memory size of the windows system on the ssd, for me, I had no more shut downs of the kernel. But the slowdown by use of to many continuous controls remains an issue.
I switched to controls using a short list of fixed values or to implement arguments of functions as step functions in order to avoid uncontrolled growth of dynamic data.
Regards Roland