"Cannot reserve JVM while holding global locks"

When using UDL, sometimes I meet "JVM while holding global locks". Why this happend?

Here is the SQL used:

create flex external table aim_track_20190210() as copy with source OssSource(path='oss://xxxxxxx20190210*') parser fjsonparser(flatten_maps=false, record_terminator=E'\n');

create table aim_track_test4 as select m1 from aim_track_20190210 limit 2000;