Help: SR HH 4 through neck problem with action

Hi, my first time on the forum. i have a problem with the action on my new SR HH through neck bass, i can’t get the action lower than 2.5 mm on the bass side with out an unacceptable amount of fret buzz, past the 12th, I’ve spent hours and hours fine tuning the set up and its as good as it can be, i am going to take it to a tech to remedy any high frets as that is all it can be…i think, hopefully that will fix the problem but i have also noticed that when the saddle is bottomed out on the e string its still a bit over 2 mm, has anyone else out there with the through neck had these issues? its a fantastic bass, sounds awesome,i love it, i just wish i could get the action down to where i like it without issues. any thoughts and input would be great, Thanks, Martin.