copying videos from iphone 7+ to pc

hi,, i am getting the following message when trying to copying my videos from iphone7+ to my PC. if you copy the first video it may work then the 2nd i get an error " a device connected to the system is not working" i restart the phone and again i copy one video, it works the 2nd video fail. it is the same for small video like 40mb or large like 250MB. knowing i used to copy videos before normally. as for photos it is getting copied without any pb. thanks for your help.