Here is imapsync 1.977 on host privremena, a linux system with 18.9/31.3 free GiB of RAM
with Perl 5.28.1 and Mail::IMAPClient 3.42
Transfer started at Thu Nov  5 00:18:42 2020
PID is 16611 my PPID is 16610
Log file is LOG_imapsync/2020_11_05_00_18_42_956_admin123_.txt ( to change it, use --logfile path ; or use --nolog to turn off logging )
Load is 0.34 0.26 0.37 1/1184 on 2 cores
Current directory is /root/imapsync-master
Real user id is root (uid 0)
Effective user id is root (euid 0)
$RCSfile: imapsync,v $ $Revision: 1.977 $ $Date: 2019/12/23 20:18:02 $ 
Command line used, run by /usr/bin/perl:
./imapsync --addheader --automap --user1 admin123
Temp directory is . ( to change it use --tmpdir dirpath )
Under cgi context
Umask set with 0077 (was 0022)
REMOTE_ADDR is ::ffff:194.166.59.157
HTTP_REFERER is http://148.251.112.220:8080/
HTTP_USER_AGENT is Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.183 Safari/537.36
SERVER_SOFTWARE is ./webserver
SERVER_PORT is 8080
kill -QUIT 16611 # special behavior: call to sub catch_exit
kill -TERM 16611 # special behavior: call to sub catch_exit
kill -INT 16611 # special behavior: call to sub catch_reconnect
kill -HUP 16611 # special behavior: call to sub catch_print
kill -USR1 16611 # special behavior: call to sub toggle_sleep
File ./imapsync__admin123__.pid does not exist
Error reading file ./imapsync__admin123__.pid : No such file or directory
PID file is ./imapsync__admin123__.pid ( to change it, use --pidfile filepath ; to avoid it use --pidfile "" )
Writing my PID 16611 in ./imapsync__admin123__.pid
Writing also my logfile name in ./imapsync__admin123__.pid : LOG_imapsync/2020_11_05_00_18_42_956_admin123_.txt
Info: will resync flags for already transferred messages. Use --noresyncflags to not resync flags.
Exiting after a justconnect on host(s):  
Exiting with return value 0 (EX_OK: successful termination) 0/20 nb_errors/max_errors
Log file is LOG_imapsync/2020_11_05_00_18_42_956_admin123_.txt ( to change it, use --logfile filepath ; or use --nolog to turn off logging )