So, the Reason of your problem is, that your data is Massive with 30000 submissions and 1000 columns and sheets. It is 50 MB in excel, it is massive as Excel file i believe. So when you would like to have it as JSON server cannot process it and you are having 502 errors due to the size of the data. Your solution is really simple. You can use the link below to import your data to Power BI, by limiting the number of submissions in each link. you need to duplicate that Power BI sheet “coping_mechanisms_in_abssence_of_service” and each duplicated data set will contain 12000 submissions separately. After the data is imported in 3 separate tables, you can append them in Power BI directly and use it as one sheet for your reporting.
You can increase of decrease the 12000 depending on your tests, 20000 might be fine as well, but my browser crashes after 12000 submissions. This should solve your problems i believe
https://eu.kobotoolbox.org/api/v2/assets/aEgHKW9Xs6vH2sThaGVUuB/data.json/?start=0&limit=12000
https://eu.kobotoolbox.org/api/v2/assets/aEgHKW9Xs6vH2sThaGVUuB/data.json/?start=12001&limit=24000
https://eu.kobotoolbox.org/api/v2/assets/aEgHKW9Xs6vH2sThaGVUuB/data.json/?start=24001
You also can check this topic, Power BI export - submissions limit , there was a similar issue with huge amount of data like you have
