Telnet uses CR-NUL and supports terminal type negotation, fixed virtual disk crash, debugger keyboard shortcuts are now configurable. Because of the last change, this version uses a different keyboard shortcut store, so keyboard shortcuts will be reset to defaults.
The virtual disk issue occurs when Altirra doesn't notice that the file has been updated in time. When this occurs, it's too late to correct the problem as DOS has already read and cached the directory entry for the file. This is ordinarily caught by a directory watcher, and since I wasn't able to reproduce the problem I had to diagnose it just off the minidump. I could see this issue happening if the files are coming from a source that doesn't reliably send directory change notifications, such as a network path.
Telnet appears to be a poorly standardized protocol. For instance, RFC 1123 says that CR-LF should be the default line ending... but of course, Linux telnet defaults to CR-only. Then there's RFC 1091, which points to RFC 1010 (now the IANA database) for the list of standardized terminal type names... but unsurprisingly, while DEC-VT100 is listed as one of the standard terminal type names, Linux neither accepts nor sends it and uses vt100 instead. Yay for standards.
The wonderful thing about specifications is that (a) people suck at writing them and (b) nobody follows them. Most specs are terrible in that they often don't cover corner cases, such as what should happen when a requirement is violated, and even frequently omit the most basic of information such as what byte order is used. This leads to horrors like FTP, where the directory listing format is literally whatever the server OS's 'dir' or 'ls' command produces. Then you get ones that are just difficult to read, like the XML spec, which is laid out in random order and constantly references concepts before they are defined. But hey, it's extensively hyperlinked, so you can play Choose Your Own Specification Adventure. On the other hand, the PNG specification is one of the better specifications I've read.