Strange performance issues with 10.5.9

# User@Host: user[user] @  [ip]

# Thread_id: 1000143  Schema: test  QC_hit: No

# Query_time: 13.510165  Lock_time: 0.000017  Rows_sent: 0  Rows_examined: 2

# Rows_affected: 1  Bytes_sent: 59

SET timestamp=1615541184;

update users set last_act = now(), some_field = 0 where primary_key = 99999;

...

# Time: 700101  3:00:31

# User@Host: user[user] @  [ip]

# Thread_id: 1004560  Schema: test  QC_hit: No

# Query_time: 31.031085  Lock_time: 0.000000  Rows_sent: 0  Rows_examined: 0

# Rows_affected: 0  Bytes_sent: 18446744073709547359

SET timestamp=31;

# administrator command: Change user;