To Reproduce:

1. Connect to Perforce repo/sandbox.

2. Add a new change list.

3. Open 'Version Control' window, select multiple files from the 'default' list and drag them to the new list.

4. Notice that only a single file was moved (if you drag a script it gets moved together with it's .meta file, but if you drag 3 scripts, only one (and it's meta) file gets copied, same with all binary and text files).

Can reproduce this on all versions from 4.3.4 to 5.0.0b1