I think Bertil Lintner wrote about this before--Deng Xioaping came to power in 1978, and the new regime must have pulled its support of CPB.

In any case Deng was more interested in his economic reforms which were highly successful.

https://www.irrawaddy.com/from-the-archive/how-ne-wins-diplomacy-weakened-burmas-communists.html

The old Burmese communists like Ba Thein Tin and Brigadier Kyaw Zaw could not do anything, anyway.