Peculiar phenomenon involving Vim on DECUServe through PuTTY

Whenever I connect to DECUServe (EISNER::) using PuTTY under
Windows, Vim takes up to well over a minute or so to come up;
each time, regardless if it's a preexisting or new file.
However, when I connect through a regular "Windows Terminal"
(PowerShell or otherwise) SSH session, Vim comes up normally,
i.e. within a second or so.
Could it be that PuTTY (since a certain version?) provides
confusing terminal type information; and, if so, how to
check/verify this?  At the same time, even if the case, I
never or rarely encountered this in the past.
  - MG