To check the table configurations for EF Core 3.1, I did the following and it helped identify issues.

It iterates all tables in the context and selects one row. If there is an exception, it will catch it and display some related information. It might be helpful to also capture the stack trace.

    public string LoopAllTables(bool stopAfterFirstFail)
    {
        var exceptions = new StringBuilder();
        var propertyInfos = _dbContext.GetType().GetProperties().OrderBy(o => o.Name).ToArray();
        foreach (var propertyInfo in propertyInfos)
        {
            var property = propertyInfo.GetValue(_dbContext);
            if (property is IQueryable<object> tableQ)
            {
                try
                {
                    tableQ.Take(1).Load();
                }
                catch (Exception ex)
                {
                    exceptions.AppendLine(ex.Message + Environment.NewLine + "  from " + 
                       propertyInfo.Name);
                    if (stopAfterFirstFail)
                    {
                        break;
                    }
                }
            }
        }

I just used parallel tasks to decrease the time a process took from over an hour to about 2 minutes.  I was wary of creating so many database contexts, but it paid off in a major way!

See the snippet of code below to see how I used the Parallel.ForEach.  .Net created almost 100 threads during the execution.

Parallel.ForEach(qry, issue =>
{
	using (var _db = new WCO())
	{
		dobType dob;
		List<dobType> birthdays = new List<dobType>();

		foreach (
			var subIssue in
				issue.DOBValue.Trim().Split(new string[] { " TO ", " to ", "-", " - " },
					StringSplitOptions.RemoveEmptyEntries))
		{
			string valueToTest = subIssue;

			// Try Month Year regex
			if (tryDateFirstPart(valueToTest, out dob))
			{
				logger.Info(string.Format("Parsed {0} to Month: {1}, Day {2} Year: {3}", issue,
					dob.month,
					dob.day, dob.year));
				saveParseDOB(dob, issue, _db);
			}
			else
			{
				logger.Error(string.Format("Could not parse {0}", issue.DOBValue));
			}
		}

	}
});

If you need someone with my ability to decrease processing times on a full time basis, please contact me through LinkedIn 

Have a great day!