Update 8.5.5 to 8.6.0

Hello all,
during the migration from 8.5.5 to 8.6.2, on first steep (8.5.5 to 8.6.0) i have this error:
2020-10-12 12:16:41.949 ***** ERROR ***** [V8.5.5] Exception-[23505] SQLSTATE[23505]: Unique violation: 7 ERREUR: la valeur d'une clé dupliquée rompt la contrainte unique « planningmode_pkey »
DETAIL: La clé « (id)=(16) » existe déjà.
2020-10-12 12:16:41.949 ***** ERROR ***** [V8.5.5] For query : UPDATE planningmode set id=16 where id=15;
2020-10-12 12:16:41.949 ***** ERROR ***** [V8.5.5] Strack trace :
2020-10-12 12:16:41.949 ***** ERROR ***** [V8.5.5] #0 Sql->query called at [/home/projtma/public_html/db/maintenanceFunctions.php:71]
2020-10-12 12:16:41.949 ***** ERROR ***** [V8.5.5] #1 runScript called at [/home/projtma/public_html/db/maintenance.php:111]
2020-10-12 12:16:41.949 ***** ERROR ***** [V8.5.5] #2 include called at [/home/projtma/public_html/tool/loginCheck.php:143]
2020-10-12 12:16:41.949 ===== TRACE =====
2020-10-12 12:16:41.949 ===== TRACE ===== Error # 1 => SQL error while executing maintenance query for version V8.6.0 (see above message)
2020-10-12 12:16:41.949 ===== TRACE =====
2020-10-12 12:16:41.949 ===== TRACE ===== *************************************************
2020-10-12 12:16:41.949 ===== TRACE =====
2020-10-12 12:16:42.015 ===== TRACE ===== 0 lines updated into table "planningelement".
2020-10-12 12:16:42.018 ===== TRACE ===== Table "leavetype" altered.
2020-10-12 12:16:42.020 ===== TRACE ===== Table "delivery" altered.
2020-10-12 12:16:42.021 ===== TRACE ===== 1 lines inserted into table "reportparameter".
2020-10-12 12:16:42.022 ===== TRACE =====
2020-10-12 12:16:42.022 ===== TRACE ===== DATABASE UPDATED
2020-10-12 12:16:42.022 ===== TRACE ===== WITH 1 ERROR
2020-10-12 12:16:42.022 ===== TRACE =====
2020-10-12 12:16:42.023 ===== TRACE ===== =====================================

This error is a problem ?
Very thanks.
Bruno.