Error trying to change site name

In Admin area -> Settings -> Site, when I try to set a new address this error is show:

Error 500 Internal Server Error
Something went wrong: [DwE500REX]

java.lang.RuntimeException: This statement modified 0 rows but should have touched exactly one row: 
      update hosts3 set canonical = 'D'
      where site_id = ? and canonical = 'C'
       [DwE8FUM1]
	at com.debiki.core.Prelude$.die(Prelude.scala:138)
	at com.debiki.core.Prelude$.dieIf(Prelude.scala:152)
	at com.debiki.dao.rdb.RdbSiteTransaction.runUpdateExactlyOneRow(RdbSiteTransaction.scala:296)
	at com.debiki.dao.rdb.RdbSiteTransaction.changeCanonicalHostRoleToExtra(RdbSiteTransaction.scala:776)
	at debiki.dao.SiteDao.$anonfun$changeSiteHostname$1(SiteDao.scala:332)
	at debiki.dao.SiteDao.$anonfun$changeSiteHostname$1$adapted(SiteDao.scala:324)
	at debiki.dao.SiteDao.$anonfun$readWriteTransaction$2(SiteDao.scala:175)
	at com.debiki.core.DbDao2.readWriteSiteTransaction(DbDao2.scala:67)
	at debiki.dao.SiteDao.$anonfun$readWriteTransaction$1(SiteDao.scala:175)
	at debiki.dao.SiteDao$.synchronizeOnSiteId(SiteDao.scala:471)
	at debiki.dao.SiteDao.readWriteTransaction(SiteDao.scala:174)
	at debiki.dao.SiteDao.changeSiteHostname(SiteDao.scala:324)
	at controllers.SettingsController.$anonfun$changeHostname$1(SettingsController.scala:76)
	at scala.Function1.$anonfun$andThen$1(Function1.scala:57)
	at ed.server.http.PlainApiActions$$anon$1.runBlockIfAuthOk(PlainApiActions.scala:422)
	at ed.server.http.PlainApiActions$$anon$1.invokeBlockAuthViaCookie(PlainApiActions.scala:244)
	at ed.server.http.PlainApiActions$$anon$1.invokeBlock(PlainApiActions.scala:133)
	at ed.server.http.PlainApiActions$$anon$1.invokeBlock(PlainApiActions.scala:91)
	at play.api.mvc.ActionBuilder$$anon$10.apply(Action.scala:425)
	at ed.server.http.PlainApiActions$$anon$1.$anonfun$composeAction$1(PlainApiActions.scala:105)
	at ed.server.http.SafeActions$ExceptionAction$.invokeBlock(SafeActions.scala:115)
	at ed.server.http.SafeActions$ExceptionAction$.invokeBlock(SafeActions.scala:82)
	at play.api.mvc.ActionBuilder$$anon$10.apply(Action.scala:425)
	at play.api.mvc.Action.$anonfun$apply$2(Action.scala:97)
	at play.api.libs.streams.StrictAccumulator.$anonfun$mapFuture$4(Accumulator.scala:183)
	at scala.util.Try$.apply(Try.scala:213)
	at play.api.libs.streams.StrictAccumulator.$anonfun$mapFuture$3(Accumulator.scala:183)
	at scala.Function1.$anonfun$andThen$1(Function1.scala:57)
	at scala.Function1.$anonfun$andThen$1(Function1.scala:57)
	at play.api.libs.streams.StrictAccumulator.run(Accumulator.scala:222)
	at play.core.server.AkkaHttpServer.$anonfun$runAction$4(AkkaHttpServer.scala:427)
	at akka.http.scaladsl.util.FastFuture$.strictTransform$1(FastFuture.scala:41)
	at akka.http.scaladsl.util.FastFuture$.$anonfun$transformWith$3(FastFuture.scala:51)
	at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:64)
	at akka.dispatch.BatchingExecutor$AbstractBatch.processBatch(BatchingExecutor.scala:55)
	at akka.dispatch.BatchingExecutor$BlockableBatch.$anonfun$run$1(BatchingExecutor.scala:91)
	at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
	at scala.concurrent.BlockContext$.withBlockContext(BlockContext.scala:85)
	at akka.dispatch.BatchingExecutor$BlockableBatch.run(BatchingExecutor.scala:91)
	at akka.dispatch.TaskInvocation.run(AbstractDispatcher.scala:40)
	at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(ForkJoinExecutorConfigurator.scala:44)
	at akka.dispatch.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
	at akka.dispatch.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
	at akka.dispatch.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
	at akka.dispatch.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)

I have checked the database and it is empty:

talkyard=# select * from hosts3;
 site_id | host | canonical | ctime | mtime
---------+------+-----------+-------+-------
(0 rows)

My deploy is using docker-compose with automatic upgrades. I think the first version was v0.6.43-b2528e2, but I'm not sure because previous VM broke and we recovered a backup.