Replace it with something non-Heki if you can. I'd look at the Arctic Tern. The Heki is a great concept, with **** implementation.
If only a Heki will fit, buy one out of Britain or Germany. Even with DHL air shipping it will cost substantially less than from Dometic, and will get there in 3 days rather than 3 months. Look on ebay.uk or ebay.de.
In the Heki Midi, there are three models: the lever operated, crank operated and electric. When I replaced mine I went with the crank model. It is perhaps a little less fragile, but the big plus is you can open and close the dome while the screen is closed. On the lever version, you first must open the screen, let all the mosquitoes in, close the dome locking them inside, then close the screen again.
Bigfoot 10.4E, 2015 F350 6.7L DRW 2WD, Autoflex Ultra Air Ride rear suspension, Hellwig Bigwig sway bars front and rear