If arm tefillin loosened before putting on head tefillin, must one recite a new blessing before retightening?

Synopsis

The Mechaber distinguishes: if arm tefillin loosened before putting on head tefillin, retighten without a new blessing (the first blessing still covers both). If arm tefillin loosened after head tefillin was already on, retighten and recite a new blessing.

Early Acharonim
Lenient
Strict
Lesser cited
Major authority

Discussion

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