Which i added to "Digest DOS Verenigingen - sector PO/VO".
http://feed.informer.com/digests/YRC5ODUWBM/feeder.rss

I added the RSS feed from this digest to "Digest DOS PO nieuwsbrieffeed" http://feed.informer.com/digests/SIYHYJVJDH/feeder.rss

It seems pubdates from items in the feed are changing

When it enters the first digest it is:
<title>Slob krijgt lijst met verbeterpunten medezeggenschap – PO/VO</title>
<link>https://www.vosabb.nl/slob-krijgt-lijst-met-verbeterpunten-medezeggenschap/</link>
<source url="https://www.vosabb.nl/nieuws/">Nieuws - VOS/ABB</source>
<guid isPermaLink="false">urn:uuid:90ce854f-d365-47f4-b4e4-93db23a2595c</guid>
<pubDate>Sat, 06 Mar 2021 19:11:19 +0100</pubDate>

and when the item is published through the digest feed in the second digest it is:
<title>Slob krijgt lijst met verbeterpunten medezeggenschap – PO/VO</title>
<link>https://www.vosabb.nl/slob-krijgt-lijst-met-verbeterpunten-medezeggenschap/</link>
<source url="http://feed.informer.com/digests/EGK8Y5LIGK/feeder">Digest DOS zoekfilter - PO</source>
<guid isPermaLink="false">urn:uuid:9feb1156-77d9-0415-67a5-ae22a0f4d1e1</guid>
<pubDate>Sat, 03 Apr 2021 02:00:00 +0200</pubDate>

What is happening here? How can I prevent this? Hope you can help me. Thanks in advance!
Henk