Best way to tackle this problem is to break it down in steps. Firstly, can you please explain at what stage in your process, you are getting the OLE error?
According to the screenshot you sent, at this stage the Invoice template is not retrieving any invoices so the number of transactions shouldn’t be a factor. So it is important for us to understand at what stage in your process the error is popping up.
In the mean time with regards to the OLE error below is an article explaining why a user would typically get an OLE error.