disconnecting USB modem

hi,

i have some trouble with ofono when i disconnect my USB modem. each time i disconnect/reconnect USB, ofono create a new modem.. 1st is /sierra_0
2nd /sierra_1
...

if i list modems, only the last connected is reported.

if i switch online/offline/enable/disable/etc.. properly the pb is still here.

is there any reason for this? or it is a bug somewhere in ofono/driver ?

thank you all !