Problems concerning download of detailed user overviews

[Tschulie]

We cannot download any detailed user overview (or the whole for all participants at one moment) in our huge runs (short runs with one up to 10 run buttons work).

It does not depend on the data format and it is not important too, how long the detailed overviews are. Sometimes we just get a white page but no download starts. But sometimes we get this HTTP Error 500:

Fatal Error

A fatal error occured and your request could not be completed. Contact site admins with these details
Error [1] in /var/www/formr.org/vendor/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Collection/Cells.php line 400
Allowed memory size of 134217728 bytes exhausted (tried to allocate 18874368 bytes)

It seems to me, that this is a internal problem that's why I opened this issue.

Thanks!
Jules

PS: We to this error in different browsers too. So it seems to be a general issue.