I found the reason of the bug:
In line 27441 of elogd.cxx the http_user is overwritten by the user saved in the sid_ array as a sideeffect of the sid_check function:
sid_check(getparam("sid"), http_user)

It can solved by changing elogd.cxx @ line 27441

27441c27441,27446
<          if (!sid_check(getparam("sid"), http_user)) { /*  if we don't have a sid yet, set it */
---
>          i=sid_check(getparam("sid"), thumb_name);
>          if (i && strcmp(http_user,thumb_name)!=0) {  /* user changed */
>             sid_remove(getparam("sid"));
>             i=FALSE;
>          }
>          if (!i) { /*  if we don't have a sid yet, set it */

Remark: I have used the variables i & thumb_name of the function in a local context.