We all get an occasional problematic tefilin or mezuza with "SENTIMENTAL" value.
I have heard in name of rav wosner that if we have tefilin from a very prominent sofer then even a bdieved is lechatchila-if I am correct he said it regarding shrt lameds in rav Nachman papirnes ksav from his older years.
The Shaila is what is the Lomdis Is it that we may use a bdieved if the chashivas of the sofer is so great or that since a chushiver sofer wrote it we count it as lechatchila.
The meuzah or that has sentimental value
is this a reason to allow a bdieved? maybe since it was written without tagim it should be kept in the china closet for sentimental value.