error when want to close activity

When I want to close an activity, i have this message on red screen and on log file:

2020-09-28 11:03:46.216 ***** ERROR ***** [V8.6.1] Exception-[23000] SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '804326' for key 'PRIMARY'
2020-09-28 11:03:46.216 ***** ERROR ***** [V8.6.1] For query : insert into historyarchive (select * from history where refType='Assignment' and refId in ((select id from assignment where refType='Activity' and refId=1218)))
2020-09-28 11:03:46.216 ***** ERROR ***** [V8.6.1] Strack trace :
2020-09-28 11:03:46.216 ***** ERROR ***** [V8.6.1] #0 Sql->query called at [/var/www/projeqtor/model/persistence/SqlElement.php:1698]
2020-09-28 11:03:46.216 ***** ERROR ***** [V8.6.1] #1 SqlElement->updateSqlElement called at [/var/www/projeqtor/model/persistence/SqlElement.php:1126]
2020-09-28 11:03:46.216 ***** ERROR ***** [V8.6.1] #2 SqlElement->saveSqlElement called at [/var/www/projeqtor/model/persistence/SqlElement.php:790]
2020-09-28 11:03:46.217 ***** ERROR ***** [V8.6.1] #3 SqlElement->save called at [/var/www/projeqtor/model/ActivityMain.php:613]
2020-09-28 11:03:46.217 ***** ERROR ***** [V8.6.1] #4 ActivityMain->save called at [/var/www/projeqtor/tool/saveObject.php:110]

Hello,

Indeed is an issue, tocket #5000 as recorded on roadmap.
The corection will be available in 8.6.2