It's not just you. And you're on PAL hardware, correct? Heck I had a really hard time just getting his modem to connect to BBSes in 64Door. Oftentimes it would call then just disconnect. Almost like how it might if you forget to add the port number at the end.After a while the system will seem to freeze altogether (I assume a really extended wait for the characters to catch up) until the BBS kicks me for no interaction, this may be worse if I type fast, I may be able to avoid it if I type slow - I haven't tried that yet. Sometimes characters just repeat across the screen for no reason.
I have had this exact same issue you're describing with the WiModem232 and 64Door. I have not had any issues at all running a "normal" terminal in ANSI mode. But for whatever reason, Jim's modem (something in the firmware) just doesn't like 64Door at all. I've moved back over to Paul Rickards modem for hitting PETSCII boards on an Amiga. It simply never has any issues at all. And I've moved Jim's modem over as my main backup. I can get online, hit my router, fire up terminal programs in ANSI and do whatever. But something about 64Door gums up in the WiModem232. Kind of a bummer. If I didn't have Paul's modem working flawlessly I'd blame the software. But since it does work it's a head scratcher. I tried various settings and finally just gave up. I was hanging BBSes over and over (sysops said it was fine - keep testing) but I after a couple of days figured, nah. I'm done doing that.
So, if you're going to hit Particles or the dozen other boards you like running off of C64s/128s, you're probably best off using your C64 for now. His modem for C64 rocks. The only issue I ever saw in that department was sometimes it would get laggy or freeze if I typed too quickly (and usually on a long-ish post). Luckily it isn't that easy to be a speedy typist on the C64. Hah!