Whatsapp videos not downloading on phone with high speed internet.

some videos from a particular sender does not download on WhatsApp on my phone. SAMSUNG GALAXY J2 2018 ANDROID VERSION 7.1.1

when trying to open that paticular video on WhatsApp web it says video not available on phone.

tried uninstalling and reinstalling WhatsApp..still no change..

This has been going on for some time
(maybe for a couple of weeks)and on one device only...WhatsApp on other devices in my household are working fine.

I turned on media visibility in Chat settings on my phone...but the issue still persists.

Although like i mentioned.. this issue occurs from videos sent from one particular sender in a WhatsApp group...

Videos from all other senders in this group and other groups and other personal chats on WhatsApp downloads properly without any problem.

I ejected the SD card from my device and checked..still same story..

I noticed now that if the mobile data is switched on instead of the Wi-Fi (72 mbps speed) at the time of receiving the video it does get downloaded.

Although if Wi-Fi is switched on at the time the video is received on my phone the video does not even download/open.. Even if trying to open it later using mobile data

green circle will come and then i get the message "download cannot be completed" also when the video is received on my phone..the file size is not displayed on the video

Would you be able to help me with this?