CardDAV sync broken

REPRODUCIBILITY (% or how often): 100%
BUILD ID = OS VERSION (Settings > About product): 4.0.1.48
HARDWARE (XA2, Xperia 10…): Xperia X
UI LANGUAGE: de
REGRESSION: (compared to previous public release: Yes, No, ?): yes

DESCRIPTION:

no more contacts from CardDAV server appear in contacts.

PRECONDITIONS:

Update to 4.0 pre release, then to 4.0.1.48. CardDAV server is radicale on a raspberry pi, it works for other devices and used to work with sailfish os version 3.x

STEPS TO REPRODUCE:

  1. wipe all contacts
  2. start new sync
  3. reboot phone
  4. start contacts
    also tried to delete the account, reinstalled it, but no success.

EXPECTED RESULT:

all contacts from all sources should be synced. If a sync fails, errors should be reported.

ACTUAL RESULT:

Contacts from CardDAV are missing, others are there. No errors are reported at all.

ADDITIONAL INFORMATION:

(Please ALWAYS attach relevant data such as logs, screenshots, etc…)