Extrude Problems

With Octoprint I have the problem that at long printing times sometime the printer "unloads" the filament in the middle of the print. The pressure then continues as normal, but the extruder does not support filament any more, since it has simply been ejected. I have Octoprint running on a notebook with an Intel i5 with 8Gb memory under Kubuntu. My printer is a Hephestos 2. If I do not happen from SD card prints. Does anyone have an idea what this could be? My Slicer is Cura 4.0
Best regards Frank

@Frank, We need more information if we are to help. Specifically, all the version numbers and log files listed below.

Additional information about your setup (OctoPrint version, OctoPi version, printer, firmware, octoprint.log, serial.log or output on terminal tab, ...)

Both the initial creation of this post and any replies will show a Need help? with multiple links detailing how to find version numbers and relevant log files.

You need to reproduce the problem and then collect the log files and post them here.