Error . Yesterday I installed a small portable using M-A to replace an old Linuxmint installation. Nothing special, all normal, but the "Error  phantom" appear another time: impossible to install the KDE Full.
I tried 3 times, no way. Really close to the desperation (almost...) I choose to install XCFE Full and... no error. Redo the same with LXQT, no error. Retry with KDE Full: ERROR!
At that point I create a small USB Key (16Gbyte) dedicated to m-a, to replace the "old" ISO image USB Key and... KDE Full is installed perfectly without any problem!
I suspect that, when m-a is used as iso image installed on a USB Key, there is a problem of disk space when installing complex environment like KDE Full. Just an idea, but confirmed from the behaviours of the previous test