I don't know what has changed to make this start happening, and it is a bit puzzling why a DVD plays once first, and then this issue happens.
However, the image you posted shows that the folder containing the DVD movie sub-directories is being opened, and not the VIDEO_TS folder. That is, the "H:\BORG_MCENROE" is being opened, instead of the "H:\BORG_MCENROE\VIDEO_TS" folder. That would imply to me that the [filename] field in MC has been changed to point to the parent folder of the VIDEO_TS folder, for some reason.
For example, I have a DVD of the movie "Firewall". The associated file and path name fields are;
[filename] = F:\Movies\Firewall (2006)\VIDEO_TS\VIDEO_TS.dvd;1
[filename (path)] = F:\Movies\Firewall (2006)\VIDEO_TS\
[filename (name)] = VIDEO_TS.dvd;1
If the [filename] was set to "F:\Movies\Firewall (2006)\", then I would expect that trying to play it would open Windows Explorer, as MC would be trying to open a folder, not a file, and Windows Explorer is the default method of opening folders.
However, MC doesn't allow me to set [filename] to "F:\Movies\Firewall (2006)\". It reverts the change. Well, actually it changes [filename] to "F:\JRiver MC AMINTHA Local Media\Movies\Firewall (2006)\VIDEO_TS\VIDEO_TS.IFO;1" when I try to do it. But that is an alternate way of addressing a DVD movie, so it still plays the movie correctly.
Check the MC fields that I mention above for a problem movie and see if they are still correct. If not, then you have a mystery to solve; How did those fields get changed?
If they are correct, try selecting a problem movie in MC Standard View, then right-clicking on it and selecting "Locate > On Disk (external)" and see if that correctly opens the VIDEO_TS folder, and not, for example, the BORG_MCENROE folder.
PS: Does the movie play correctly if you try to start it from within Standard View?