The answer is yes. There is a monastery of cloistered Benedictine nuns in Quebec that were formerly nuns of the Precious Blood. One or two left, but the majority voted to make the change of orders.
Other monasteries have changed their commercial focus, one monastery I know has changed from lithography to beer-making. Lastly, yes they can change their observances within the context of their rule. For example a Benedictine monastery could adopt a different approved schema for their Divine Office. Such was done by the house I’m affiliated with in the '80s.
Lastly, again a house could chose to adopt the TLM, or go the other way as well.
It’s an internal house matter really, it’s the same as any decision you make in your family. It’s nobody else’s business. You may never know the actual reasons for a change, such things are decided in chapter and the ultimate decision lies with the abbot, at least in the Benedictine order, or the Superior General in some cases of other orders.