Index – ready but 11619 in backlog

We have a indexer in Magento 2.3.3 that is giving us a difficult time.

We tried many times reset and reindex that indexer but does not help.

| Bol.com Offer Export | Ready | Schedule | idle
(11619 in backlog) | 2020-01-18 19:31:42 |

So this is from extension https://marketplace.magento.com/honl-bol-com-retailer.html

We tried many times :

php bin/magento indexer:reset bol_offer_export

and then

php bin/magento indexer:reindex bol_offer_export  

But no luck at all. Any ideas on this ?