I cant delete files/Images in mobile as above mentioned.Whenever I delete particular file/image it shows a dialog containing error that
libmtp error: could not delete object.
Which version of Ubuntu are you running?
Perhaps you do not have the right
MTP packages installed on your system?
sudo apt-get install mtp-server libmtpserver-dev
Also I've seen cases when it failed and renaming the file did the job (kinda strange). In case you want to go that way.