Not a user of their software. If you have not contacted the software vendor for suggestions, do so. They are the experts on their software...
All I can offer is a programmer's perspective. Any sort of data input, when the data must remain open for changes in another location, as well as updated with changes on your end, and at any other location, has to be slow. Data collision is the issue (who has the latest, and when, and what to do if more than one tries to change the same piece at the same time). Testing for data collision is slow, as is keeping all possible parties updated in a live manner.
Slow is a relative term. Even I can type faster than data can safely be shared, but a two finger typist may not have enough speed to notice the time taken for data updates and security.