5Paisa

For security listed on NSE and BSE, same-day trades reflect under NSE positions, even if it was traded on BSE. The position is tradeable on either exchange.

Groww

On complete sell of security, holdings data for that security becomes unavailable before settlement. Position information is available as expected.

{
   "holdings": {
       "quantity": 20,
       "averagePrice": 167.90
   },
   "positions": {
       "nse": {
           "quantity": 0,
           "averagePrice": 0
       },
       "bse": {
           "quantity": 0,
           "averagePrice": 0
       }
   },
   "nseTicker": "ONGC",
   "bseTicker": "ONGC",
   "name": "Oil and Natural Gas Corporation Ltd",
   "isin": "INE213A01029",
   "transactableQuantity": 0,
   "smallcaseQuantity": 0
}

{
   "holdings": { // ideally, data should be returned until trade is settled
       "quantity": 0,
       "averagePrice": 0
   },
   "positions": {
       "nse": {
           "quantity": -20,
           "averagePrice": 167.85
       },
       "bse": {
           "quantity": 0,
           "averagePrice": 0
       }
   },
   "nseTicker": "ONGC",
   "bseTicker": "ONGC",
   "name": "Oil and Natural Gas Corporation Ltd",
   "isin": "INE213A01029",
   "transactableQuantity": 0,
   "smallcaseQuantity": 0
}

IIFL

Positions are not available just yet. quantity & averagePrice will be 0 always
holdings.averagePrice is not available just yet (this is now available)

{
   "holdings": {
       "quantity": 20,
       "averagePrice": 23.43 //now available
   },
   "positions": { // not available
       "nse": {
           "quantity": 0,
           "averagePrice": 0
       },
       "bse": {
           "quantity": 0,
           "averagePrice": 0
       }
   },
   "nseTicker": "ONGC",
   "bseTicker": "ONGC",
   "name": "Oil and Natural Gas Corporation Ltd",
   "isin": "INE213A01029",
   "transactableQuantity": 20,
   "smallcaseQuantity": 0
}

Motilal Oswal

~~On T+1, the security is incorrectly listed under holdings array (with quantity 0) and not under positions. The holdings quantity is eventually rectified once security is settled in Demat account.~~ (this is now resolved)
For MOSL, if a user is holding stocks, that are part of paid only portfolios of MOSL (IAP: which is essentially a sub-port of MOSL advisory), then those particular holding's quantities will not be available in the holdings import response, since those are blocked from selling.

Upstox and AliceBlue

On T+1, the securities bought from BSE will also reflect under the holdings array (rather than positions array), but it won't be transactable. It becomes transactable only once settled in Demat account.