ubuquity crashes in 15.10

now i tried different and put an ubuntu lts-14.04 LTS on the 4th partition from windows, pendrive, i.e. an iso. i then booted this ubuntu LTS and wanted to install ubuntu on the other 3 partitions, as above. now the installer says (i cannot copy the text unfortunately ...):

failed to unmount partitions
the installer needs to commit changes to the partition tables, but cannot do so because partitions on the following mount points could not be unmounted:
/cdrom

there the installer is right, because i booted from there. but i am wondering why the installer wants to commit anything if i do not change a single one of the partitions.

root@ubuntu:~# lsof /cdrom
lsof: WARNING: can't stat() fuse.gvfsd-fuse file system /run/user/999/gvfs
      Output information may be incomplete.
root@ubuntu:~# mount | grep cdrom
/dev/sdb1 on /cdrom type vfat (ro,noatime,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro)

not sure if this is not the same than #313452 supposedly fixed years ago ?

bug313452 i mean

This still exits in 16.04 and it is impossible to install the EFI repertory in /EFI of this partition. However it is possible to use another partition. butn after finish the installation, it is not possible to copy on these partition because
ubuntu@ubuntu:/$ ls /cdrom
ubuntu@ubuntu:/$ sudo mount -v /dev/sda1 /mnt/A
mount: /dev/sda1 is already mounted or /mnt/A busy
ubuntu@ubuntu:/$ ls /mnt/A
ubuntu@ubuntu:/$ fuser /dev/sda1
ubuntu@ubuntu:/$

For me, this solution is not good
See. http://www.hostingpics.net/viewer.php?id=449892Screenshotfrom20160521124220.png

PS: I use also a USB drive to install ubuntu.
On EFI, i have a big problem: It is necessary to replace /EFI/BOOT/bootx64.efi by /EFI/ubuntu/grubx64.efi for booting with an external drive. So i use windows10 to do this!

Thank you for taking the time to report this bug and helping to make Ubuntu better. We are sorry that we do not always have the capacity to look at all reported bugs in a timely manner. There have been many changes in Ubuntu since that time you reported the bug and your problem may have been fixed with some of the updates. It would help us a lot if you could test it on a currently supported Ubuntu version. If you test it and it is still an issue, kindly upload the updated logs by running only once:
apport-collect 1502697

and any other logs that are relevant for this particular issue.

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