Opera, Portable Edition persistent aborts and corruption

For a number of Opera releases now, I am experiencing persistent Opera Portable problems that have rendered it unreliable to the point of being unuseable.

Some symptoms:
- On startup within PortableApps, Opera will start with, apparently, a fresh, initialised profile and all user settings, extensions, bookmarks will be missing. This does not correlate with any other observable changes. It does not happen following an upgrade. It just happens, frequently.

- On startup within PortableApps, Opera will fail to start and reports that there is a duplicate profile. On doing the detective work, there are indeed two profiles. We can delete one and get it going again, but there is no indication as to why this happens, and it keeps happening.

- On recent releases, and specifically the current Opera Portable 50 releases, there is a persistent, repeatable failure that leads to abort without explanation: On clicking on the top left "Opera" button and the main menu opening, if I move the mouse pointer down, option by option, and hover (not click) on various menu items, everything is normal with the exception that hovering over the "Bookmarks" item, which would normally open a sub-menu, after a delay of a couple of seconds Opera Portable aborts without a word and subsequently restarts, saying "Opera has recovered from an error" or similar. Usually there is no message; on one occasion only there was an error window indicating a permissions problem and the advice "contact the administrator of this computer". The user _is_ an administrator, and running Opera Portable as administrator made no difference - it still aborted.
Incidentally, if you do a fresh install of Opera 50, this does not initially happen. It is only after changing options from the default, and importing some bookmarks from an .html file, that this aborting behaviour starts, so a totally fresh install won't reproduce it.

This is under Windows 10, Windows 8.1, and Windows 7 on more than 3 machines.
I have completely uninstalled Opera Portable from the PortableApps USB key, verified that it is completely uninstalled, and reinstalled, many, many times. I have error-checked the USB key. I have low-level formatted the USB key (unusual I know, but I'm desperate) and have totally reloaded the PortableApps suite from scratch, more than once. This problem is defeating all efforts to fix it.

I am forced to stop using Opera Portable, which is a shame because it is a useful browser and I still use the installed version.

I have tested the legacy Opera Portable version 36 and it behaves correctly and does not exhibit any of these problems.