Speakers internally dont work A1398

Hello, i have followed all the sound advice on ifixit regarding internal speakers. Mine have been dead since updating to Catalina, however these were working when i got the machine, as replacement for my Late 2013 15" which i dropped. This has been kept sweet, and when you do a restart the bong goes muffled and then dies once it is doing the sound. the sound does not work. i assumed this was because of the update. But it doesn't appear to be. Sound does come back intermittently but can be months and it will come back for perhaps a day and then die, although not had this for months. Every thing else works fine, Bluetooth head phones work, USB sound works on my 27" monitor, likewise with the Thunderbolt ports, and the microphone. It maybe just a case of speaker replacement, however i don't think that is the issue. Sometimes i think its the mini display port as sometimes the sound comes back if you take it out really slowly. Although this has not been the case for at least 3/4 of a year. It just means that my second laptop isn't as great as my first one. I've never had this before, any ideas? My machine is the Dual Graphics 2.5ghz 16gb RAM