Hi @Andre,
It might be worth checking you have the tornado server set to accept max message size, this thread has something about it but I’m sure I’ve saw @Marc put some details together neatly somewhere. Maybe nothing to do with your issue but worth a try seeing it seems like file size problems but 5mb seems low so maybe another issue entirely…
https://discourse.holoviz.org/t/panel-fileinput-not-updating-param-parameter-value/3184