Похоже, соответствует такому багу апстрима:
https://sogo.nu/bugs/print_bug_page.php?bug_id=2298

Вот лог воспроизведения (попытка сделать put из cadaver).

Aug 17 16:08:55 sogod [16387]: 192.168.100.10 "PROPFIND 
/SOGo/dav/dod/Calendar/personal/ HTTP/1.1" 207 1315/288 0.011 - - 0
Aug 17 16:09:10 sogod [16387]: |SOGo| starting method 'PUT' on uri 
'/SOGo/dav/dod/Calendar/personal/personal.ics'
2016-08-17 16:09:10.913 sogod[16387] PG0x0x55f5d8b24c80 SQL: SELECT 
c_path4 FROM sogo_folder_info WHERE c_path2 = 'dod' AND c_folder_type = 
'Appointment'
2016-08-17 16:09:10.914 sogod[16387] PG0x0x55f5d8b24c80 SQL: SELECT 
c_folder_id, c_path, c_location, c_quick_location, c_acl_location, 
c_folder_type FROM sogo_folder_info WHERE c_path1 = 'Users' AND c_path2 
= 'dod' AND c_path3 = 'Calendar' AND c_path4 = 'personal'
2016-08-17 16:09:10.915 sogod[16387] PG0x0x55f5d8b24c80 SQL: SELECT 
b.c_name,b.c_version,b.c_creationdate,b.c_lastmodified,a.c_component,b.c_content 
FROM sogodod0027f93f507_quick a, sogodod0027f93f507 b WHERE (a.c_name = 
'personal.ics') AND a.c_name = b.c_name AND (c_deleted != 1 OR c_deleted 
IS NULL)
Aug 17 16:09:10 sogod [16387]: |SOGo| request took 0.005093 seconds to 
execute
Aug 17 16:09:10 sogod [16387]: 192.168.100.10 "PUT 
/SOGo/dav/dod/Calendar/personal/personal.ics HTTP/1.1" 404 208/0 0.006 - - 0

Если из файла вычистить все русские буквы, то его удается положить.