CGB, yes, but that is the start of a new problem.
IMHO the Chinese ship may have gained a convergence zone contact and may well not have recognised it as such. It is the sudden signal loss which is a clue.
If they held it for 15 minutes the first time, as 2 nm, then they may have been crossing the annulus. The 90 second contact may have been just clipping it.
I did post about the deep sound channel a few days ago but it was modded out.