OK glad you were able to fix the problem. Below is some deeper explanation from our Lead Developer.
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This is actually a fairly common error message, and you’ll encounter it in weird places on various Standard objects. It only ever happens for non-Admin users, because non-Admin users’ access to records is governed by the Salesforce Security Model, whereas Admins have the “View All Data” permission, which means that Salesforce ignores the Security Model completely for them when choosing which records to let Admins access. So for Salesforce’s purposes, it’s a lot more “expensive” to try to determine which records a non-Admin user should have access to, because Salesforce has to evaluate the whole Sharing Model for a given object when a non-Admin user runs a query on that object. Therefore Salesforce puts in these “Implementation Restrictions” that limit how many records of these Standard Objects that non-Admin users can request in a particular transaction. This makes sense for standard Objects like Task and Event for which there are often millions of records in customers’ orgs, because Salesforce’s Query Optimizers have to do a lot more work to try to search through these millions of records trying to find ones that a non-Admin user has access to.
