Unable to reserve EN 40476 Budapest-Berlin

Hi,

I’ve been trying to reserve seats for my wife and I on EN 40476 from Budapest to Berlin in late July and haven’t had much luck.

I first saw a recommendation to book this via oebb.at. I can book a combined ticket/reservation through that website, but if I search for reservations only, the website indicates “Ticket not available”. It’s a similar story with cd.cz and MAV -- it looks like they’ll happily sell me a pair of tickets but separate reservations aren’t available. 

Things get even weirder if I try to book it through the Eurail website directly. If I search for tickets for the two of us, I only see two options -- the seating compartment (ouch) and 2x single sleeper cabins ($$$). 

However, if I search for a ticket for one of us, I see all of the expected seat types.

These prices seem pretty high, but they are quite a bit less than the full ticket prices via oebb / MAV, so I guess this is just what a reservation costs? But regardless, I have no idea why I wouldn’t be able to choose a double sleeper cabin or a couchette when booking for the both of us together. I suppose I could reserve seats by booking individual seats twice, but I’d rather not be separated on the train because we booked separate reservations. 

I don’t think this is a case of seat availability on a specific day, because I’m getting the same behaviour when I look at trains any day in July or August. 

Has anyone successfully reserved eats on this train before? Is there something I’m missing?

Thanks!