There are performance problems when over 100 addresses are added to the Fax Phone Book. The recommendation is to actually limit the number of addresses in the phone book to 100 or less. If as many as 1000 addresses are added to the phone book the system may crash or hang.
With regard to a workaround, the only one we know of is to rename the phonebooks. You could switch from phone book to phone book by renaming the current phone book to something else, and renaming the phone book that they want to use "Fax Phone Book". This is the only known work around.
Engineering is looking into improving the Fax Phone Book in future revisions of the software. There is no additional information on what the improvements will be at this time.