Crystal filters are a known problem resulting in a deaf receiver.
Information about Kenwood TM-D710 posted on QRZ Tech Forums, 10 years ago (October 2010).
https://forums.qrz.com/index.php?threads/kenwood-tm-d710-failure-of-toko-filters.267722/
TOKO Filters: A50EE and A55EE
Kenwood part numbers for the Toko filters: L72-1034-05 ($5.66) and L72-1035-05 ($5.52)
https://www.kenwoodparts.com/parts/find
Parts Cost for BOTH Filters: $ 11.18 USD
The Mysterious Case of the Withering Filters – Tasos Thomaidis, SV8YM, July 12, 2010
http://sv8ym.blogspot.com/2010/07/mysterious-case-of-withering-filters.html
The Mystery of the Failing Filters – Julian Moss, G4ILO, September 9, 2010
http://blog.g4ilo.com/2010/09/mystery-of-failing-filters.html