Isaiah Silva -- who's in an ongoing divorce with Frances -- claims Courtney's refused to come to the door twice when his investigators tried to serve her with deposition papers. According to the docs ... she's also ducking the L.A. Sheriff's Dept.'s attempts to do the same.
Silva wants a depo from Love because he claims she has "personal knowledge of many of the facts" surrounding the 1959 Martin D-18E acoustic guitar Kurt played during Nirvana's "MTV Unplugged."
We reached out to Courtney ... her rep tells us she's already publicly stated the guitar is a family heirloom and doesn't belong to anyone other than family, which echoes what she told us in July 2016. The rep also says Courtney hasn't been home much ... she's been filming in Canada.