I am hoping to understand the cause of this and hopefully find a solution - I have looked at every possible solution, but haven't been able to fix it.

Sitecore v10.0.2 using Solr 8.4.

* In my current set up, Core DB is shared between CM and CD servers.
Index update strategy for web dB is **onPublishEndAsyncSingleInstance**
combined with **remoteRebuild**.
* I created a new item and published it. Item was published to the web
db, but the item didn't appear in the index(***but item was updated in the index when I  

set up the solr as local standalone instance***).
* I thought perhaps core db might have a play in this. So, I checked
the event queue settings to see if it was set to true & it is.
* When we trigger sitecore web index rebuild from sitecore  

interface(control panel) then only remote solr instances indexes are
getting updated.
* All the events are processed in the event queue according to  

EventQueueStats.aspx & in the event queue table as well.

What could be the cause of it?