Thanks for providing extra information about your scenario. It sounds like you are using a web form and that your form design includes nested repeats, is that right? It sounds like you also have calculations across those repeats and you are expecting multiple instances of those repeats.
Some high-level ideas you could explore, most of which are in the documentation:
- Make sure you are on the latest version of Central (use the question mark menu in the upper right corner of the screen). We've made many performance improvements to web forms recently. If you're running an older version, you may want to try your form at https://getodk.org/xlsform/ to see whether upgrading would help
- Reduce the calculations you do in the form. Can you do some in analysis instead? Can you conditionally run certain calculations (e.g. use an
ifto only calculate a sum when all values are entered) - Unroll some of the repeats (make them into groups with fixed contents)
- Split the form into multiple forms. With web forms, you could create links to the subforms and specify some default values for them. There is not much documentation around this because we'd like to improve the implementation but you can see how to do it today here.
- If respondents have Android phones, try Collect and see if it performs better.
It would be helpful if you're able to share your form so we can make more specific recommendations and also use it as a target for performance improvements. If you can't share it publicly you could message it directly.