Triggers are not firing when a record is queried, but formula fields are recalculated. This error is normally happening, if the SOQL query to get record information, exceeds the character limit of 20K.
I can make an assumption, that the Account object has a big number of custom fields (more than 250) and some of them can be pretty complicated formula fields.
Actually, as of Sept. 2021, it turns out you can.
Salesforce's documentation isn't very clear on this. You can't edit the update reminder entries themselves, but you CAN turn update reminders on and off.
The relevant settings are in settings/Opportunity.settings-meta.xml:
You are setting an incorrect API name for the lead source field on the Lead object. Change $field_name = 'source__c'; to the :
$field_name = 'LeadSource';
you can reference the following documentation to check all API names for fields on Lead object SOAP API Developer Guide Lead