ecloud Notes Sync is broken

/e/ version: e-20-20211208150509-dev
Device model(s): not deice-specific
Device rooted: yes/no

Summary

Synching Notes between device and ecloud.global is failing. Both /e/'s Notes app and NextCloud notes app fail with the error message shown below.

Both apps sync fine with other NextCloud instances (I use my.owndrive.com).

It may be an intermittent problem: testing new build with three different devices (z3, z3c, suzuran), sync eventually succeeded for z3 and z3c but failed on suzuran. It is also failing on my daily driver (lilac running custom e-0.19-q build)

File sync using NextCloud client app is fine - including the .md files in the Notes folder.

Technical informations

Relevant logs (adb logcat)

In /e/'s app I'm seeing a transient error message with a java: file not found error, which mentions notes api version 0.2

Using NextCloud notes app, I get the following error information

App Version: 3.4.16
App Version Code: 3004016
App Flavor: fdroid

Files App Version Code: 30180090

---

OS Version: 4.4.247-whatawurst+(eng.pete.20211029.064951)
OS API Level: 29
Device: G8441
Manufacturer: Sony
Model (and Product): G8441 (G8441)

---

java.lang.RuntimeException: com.nextcloud.android.sso.exceptions.UnknownErrorException: Software caused connection abort
 at io.reactivex.internal.util.ExceptionHelper.wrapOrThrow(ExceptionHelper.java:46)
 at io.reactivex.internal.observers.BlockingMultiObserver.blockingGet(BlockingMultiObserver.java:93)
 at io.reactivex.Maybe.blockingGet(Maybe.java:2321)
 at io.reactivex.Observable.blockingSingle(Observable.java:5381)
 at it.niedermann.owncloud.notes.persistence.NotesServerSyncTask.pullRemoteChanges(NotesServerSyncTask.java:219)
 at it.niedermann.owncloud.notes.persistence.NotesServerSyncTask.run(NotesServerSyncTask.java:96)
 at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:462)
 at java.util.concurrent.FutureTask.run(FutureTask.java:266)
 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
 at java.lang.Thread.run(Thread.java:919)
Caused by: com.nextcloud.android.sso.exceptions.UnknownErrorException: Software caused connection abort
 at com.nextcloud.android.sso.api.AidlNetworkRequest.performNetworkRequestV2(AidlNetworkRequest.java:172)
 at com.nextcloud.android.sso.api.NextcloudAPI.performNetworkRequestV2(NextcloudAPI.java:171)
 at com.nextcloud.android.sso.api.NextcloudAPI.lambda$performRequestObservableV2$1$com-nextcloud-android-sso-api-NextcloudAPI(NextcloudAPI.java:110)
 at com.nextcloud.android.sso.api.NextcloudAPI$$ExternalSyntheticLambda0.subscribe(Unknown Source:6)
 at io.reactivex.internal.operators.observable.ObservableFromPublisher.subscribeActual(ObservableFromPublisher.java:31)
 at io.reactivex.Observable.subscribe(Observable.java:12284)
 at io.reactivex.internal.operators.observable.ObservableSingleMaybe.subscribeActual(ObservableSingleMaybe.java:31)
 at io.reactivex.Maybe.subscribe(Maybe.java:4290)
 at io.reactivex.Maybe.blockingGet(Maybe.java:2320)
 ... 8 more