Getting error " Received server error LOCKED (0x9) on packet"

I am getting this error from time to time. Can please somebody help me find the problem?

Received server error LOCKED (0x9) on packet:

The entire error is:

[Tue Sep 22 17:28:21.382044 2020] [proxy_fcgi:error] [pid 28376] [client 162.158.75.86:34522] AH01071: Got error ‘PHP message: [cb,WARN] (server L:382 I:2974473523) redacted-server-hostname:11210 (CTX=0x55d5c1857820,memcached,SRV=0x55d5c1857370,IX=0) Received server error LOCKED (0x9) on packet: OP=0x94, RC=0x9, SEQ=1PHP message: [cb,WARN] (server L:382 I:2974473523) redacted-server-hostname:11210 (CTX=0x55d5c1857820,memcached,SRV=0x55d5c1857370,IX=0) Received server error LOCKED (0x9) on packet: OP=0x94, RC=0x9, SEQ=2PHP message: [cb,WARN] (server L:382 I:2974473523) redacted-server-hostname:11210 (CTX=0x55d5c1857820,memcached,SRV=0x55d5c1857370,IX=0) Received server error LOCKED (0x9) on packet: OP=0x94, RC=0x9, SEQ=3PHP message: [cb,WARN] (server L:382 I:2974473523) redacted-server-hostname:11210 (CTX=0x55d5c1857820,memcached,SRV=0x55d5c1857370,IX=0) Received server error LOCKED (0x9) on packet: OP=0x94, RC=0x9, SEQ=5PHP message: [cb,WARN] (server L:382 I:2974473523) redacted-server-hostname:11210 (CTX=0x55d5c1857820,memcached,SRV=0x55d5c1857370,IX=0) Received server error LOCKED (0x9) on packet: OP=0x94, RC=0x9, SEQ=8’