See the below rulings:

You can change your marja by starting to refer to the edicts of the new marja and acting upon them. However, the change is permissible only if it is based on religious evidence, for example, when it is proven to you that the new marja is more knowledgeable than the current one. (Office of Grand Ayatollah Sayyid Mohammad Saeed al-Hakeem)
https://www.alhakeem.com/en/questions/799

Issue No.10- If a Mujtahid who is followed by a person, dies, one may still follow him, and if he is more learned (A'lam) than a living Mujtahid, it is obligatory (wajib) to continue to remain in his taqlid, provided that he has acted on his fatwa or at least has undertook to act, in practice, upon his edicts (Fatawas). But if the living Mujtahid is more learned than his dead Mujtahid; it is obligatory to follow the living Mujtahid.

https://www.leader.ir/en/book/32/Practical-Laws-of-Islam?sn=5238

There is a consensus that it is permissible to change if you have evidence that the person you have switched to is 'the most learned.'