Ralph, and polyglot, The Dynax 9 which I bought does not have the flash problem. The one with the problem was earlier, but I backed off as it needed a professional repair. Put first film through the 9 yesterday afternoon and all seems to be working well. The seller told me to beware of the shutter button - "like butter" he said. I am used to Minolta shutter buttons, but this one on the 9 is so smooth I fired off 2 shots accidentally.
I have the Minolta 4000 flash, with the appropriate flash shoe, which I have used on my 800si. I can use that for the 9, but will be looking for the 5400HS flash. Their price(used) is still about £100 in the UK. But it must be a very useful gun when you can use it at all speeds on the Dynax 9.