Hi everyone

I am having an issue with my code that I should not get. I definitely have more than 10,000 opportunities/accounts in production but my code should only be updating the opportunities related to the account of the event I am inserting. I am getting this error when trying to insert the event on an account with less than 20 related opportunities. Any help is appreciated thanks.

Apex Trigger: 

trigger EventTrigger on Event (before insert, before update) {
    if(Trigger.isInsert){
        list<Event> CSTIMPList = new list<Event>();
        for(Event evnt : trigger.new){
            if(evnt.Implementation_App_Type__c != null && evnt.System_Admin_Over_Ride__c != 'Mark Complete App Date'){
                if(evnt.Implementation_App_Type__c == 'CST'){
                    CSTIMPList.add(evnt);
                }
            }
        }
        if(CSTIMPList.size() > 0 && CSTIMPList != null){
            Event_HDL.updateimpdateCST(CSTIMPList);
        }
    }
}

Apex Class:

public class Event_HDL {
	public static void updateimpdateCST(Event[] evnts){
			List<Opportunity> OppList = new list<Opportunity>();
			List<Account> relatedacclist = new list<Account>();
			//map the Opportunity record
			Map<Id, List<Event>> oppIds = new Map<Id, List<Event>>{}; 
			for(Event evnt : evnts){
				oppIds.put(evnt.WhatId, new list<Event>());
				oppIds.get(evnt.WhatId).add(evnt);
			}
			//map the account
			Map<Id, List<Opportunity>>  soaIds= new Map<Id, List<Opportunity>>{};
			Map<Id, List<Opportunity>>  accIds= new Map<Id, List<Opportunity>>{};
			for(Opportunity opp : [Select Id, AccountId, Implementation_Appointment_Date__c,
								   Account.Regarding_Review_FP__c, Account.Regarding_Review_Super__c, Account.Regarding_Review_ROA__c from Opportunity where Id in: oppIds.keySet()]){
				soaIds.put(opp.Account.Regarding_Review_FP__c, new list<Opportunity>());
				soaIds.put(opp.Account.Regarding_Review_Super__c, new list<Opportunity>());
				soaIds.put(opp.Account.Regarding_Review_ROA__c, new list<Opportunity>());
				soaIds.get(opp.Account.Regarding_Review_FP__c).add(opp);
				soaIds.get(opp.Account.Regarding_Review_Super__c).add(opp);
				soaIds.get(opp.Account.Regarding_Review_ROA__c).add(opp);
				accIds.put(opp.AccountId, new list<Opportunity>());
				accIds.get(opp.AccountId).add(opp);
			}
			//update the related account with the new imp app date
			for(Account acc : [Select Id from Account where Id in: accIds.keySet()]){
				for(Event evnt : evnts){
					acc.CST_Implementation_Appointment_Date__c = evnt.StartDateTime;
				}
				relatedacclist.add(acc);
			}
			if(relatedacclist.size() > 0 && relatedacclist != null ){
				update relatedacclist;
			}
			//update all cst soas and recommendations(only from the latest review) off the back of them with the new imp app date
			for(Opportunity opp : [Select Id from Opportunity where Related_SOA__c in: soaIds.keySet() OR Id in: soaIds.keySet()]){
				for(Event evnt : evnts){
					opp.Implementation_Appointment_Date__c = evnt.StartDateTime; 
					opp.Trust_Deed_Date__c = evnt.StartDateTime;
					opp.Trust_Deed_Appointment_Date__c = evnt.StartDateTime;
				}
				OppList.add(opp);
			}
			
			
			//update the opportunities
			if(OppList.size() > 0 && OppList != null){
				update OppList;
			}
			
			
	}
}