I don’t see such problem and I can use USB AT port to do AT communication afterwards:
ati3
HL7812.5.7.3.0
OK
at+kusbcomp?
+KUSBCOMP: 0,0,0,0
OK
at+switracemode?
+SWITRACEMODE: RnD,9,2,0
OK
AT+KUSBCOMP=1,1,2,3
OK
at+cfun=1,1
OK
I would suggest to enable RnD port in UART0 with AT+SWITRACEMODE command so that you can still enter AT command via UART0 port throughout your testing
e.g.
at!unlock="A710"
OK
at+switracemode?
+SWITRACEMODE: RnD,9,2,0
OK
at+switracemode=RnD
OK
at+switracemode?
+SWITRACEMODE: RnD,9,2,0
OK