Primeng p-table virtual scroll display previous rows when using row grouping

I'm trying to create a p-table that has grouped rows but I'm not able to correctly apply the virtual scroll feature.

p-table is part of the PrimeNg framework.

The issue is when scrolling and doing a lazy loading (which, actually is just appending some rows), the table display previous rows instead of the new ones. But if I load all my data and scroll from the beginning to the end, all rows are correctly displayed. I assume this is a problem during the refreshing of the table after a lazy load.

For a better comprehension of this issue I've reproduced it on a stackblitz: https://stackblitz.com/edit/angular6-primeng-8mtvwc

Thank you for any help.

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