Login cpanel "the connection was reset"

Hello, we move accounts from one server to other server. After transfer accounts and sites worked good. Today, user of one account don't can access in your cpanel account, get "the connection was reset".
We try login with us reseller account in cpanel, navigate on all account and work fine with exception of this account, we get "the connection was reset".
If try change password of this user, we get,
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exit level [die] [pid=43750] (Failed to change RUID from “0” to “0”: Resource temporarily unavailable)
at /usr/local/cpanel/Cpanel/ForkAsync.pm line 39.
Cpanel::ForkAsync::do_in_child(CODE(0x4585210)) called at /usr/local/cpanel/Cpanel/ForkSync.pm line 61
Cpanel::ForkSync::new("Cpanel::ForkSync", CODE(0x7156428)) called at /usr/local/cpanel/Cpanel/ForkSync.pm line 130
Cpanel::ForkSync::do_in_child(CODE(0x49036a8)) called at /usr/local/cpanel/Cpanel/AccessIds.pm line 108
Cpanel::AccessIds::do_as_user_group("XXXXXX", undef, CODE(0x45dd6e0), "XXXXXX", CODE(0x45dd6e0)) called at /usr/local/cpanel/Cpanel/AccessIds.pm line 70
Cpanel::AccessIds::do_as_user("XXXXXX", CODE(0x45dd6e0)) called at /usr/local/cpanel/Cpanel/Services.pm line 252
Cpanel::Services::signal_users_cpsrvd_to_reload("XXXXXX") called at /usr/local/cpanel/Cpanel/ChangePasswd.pm line 165
Cpanel::ChangePasswd::change_password(__CPANEL_HIDDEN__, __CPANEL_HIDDEN__, __CPANEL_HIDDEN__, __CPANEL_HIDDEN__, __CPANEL_HIDDEN__, HASH(0x71371a0), __CPANEL_HIDDEN__, __CPANEL_HIDDEN__, __CPANEL_HIDDEN__, ...) called at /usr/local/cpanel/Whostmgr/Passwd.pm line 36
Whostmgr::Passwd::passwd(__CPANEL_HIDDEN__, __CPANEL_HIDDEN__, HASH(0x71371a0)) called at whostmgr/bin/whostmgr.pl line 2141
main::passwd called at whostmgr/bin/whostmgr.pl line 773
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Any suggestion?
Thanks

 

Solved,
1. Run backup of client
2. Delete client account
3. Restore clent account from backup.
Thanks

 

The Problem persist. We and client don't can access to cpanel account of this user.
After restore, i tested if is worked and is worked fine, but today we get "The connection was reset"
In /var/log/messages there is this,
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Mar 17 18:34:30 server cagefs.command.server[172501]: Can't change process permissions to UID 557. Current user ID 0, euser ID 0, user xxxuserxxx
Mar 17 18:34:31 server cagefs.command.server[172508]: Can't change process permissions to UID 557. Current user ID 0, euser ID 0, user xxxuserxxx
Mar 17 18:34:48 server cagefs.command.server[172532]: Can't change process permissions to UID 557. Current user ID 0, euser ID 0, user xxxuserxxx
------------
csf/lfd banned ip with this log,
FAILED LOGIN cpaneld: switchuser: failed to set uid
---------
P.S. Others accounts not has this problem.
Any suggestion?

 

Thank you Michael for you reply.
We have not yet opened the ticket, we wanted to present more information in support of cpanel. We investigated the problem and we have seen that.
If we do login to cpanel user account with his login and pass, cpanel is work fine (we can change password without errors in the whm).
When user do login with his login and pass, His cpanel account is crashed and after we can not login in your account cpanel.(If we chage password in whm of this user, we get error).
We think that the problem in his browser(settings) (we transfer His account from other our server with whm/cpanel), we asked to empty the cache, cookies, and saved passwords and use other browser or other pc.
Now we are waiting for the response of our customers

 

We found the cause of problem, We use whmcs and remote login from client account.
Cause of problem is enabled option in tweak setting under security tab
Require SSL [?]
*Require SSL for all remote logins to cPanel, WHM, and Webmail. Recommended*
We use valid certificate for cpanel/webmail

 

Hi Michael,
Yes, this user has tried to access direct, and it was error. To clarify that, if I did login before user, cpanel worked. If I was login after user login, cpanel not worked.
We haved this problem with one customer, others customers had not reported