Hi,
Sounds like a classic link flap. Couple of checks to narrow down which device causes the link to flap/interface up/down/up condition.
1. When you get to know that link/interface went down & came back up, check for log in messages log file on the EX switch and know what those logs indicates.
2. Just re-check if the interface properties are same/identical on both ends(EX Huawei) such as speed/dulplex/mtu.
3. Is it possible to bypass WDM device and connect Hauwei & EX4500 directly or perhaps connect them through another node just role out WDM?
4. Ensure that fiber/copper is clean, check for bad cable/lose wire. etc..
You mentioned "any command to change the interface attributes to match with Juniper", Why change config, is this a new/setup configuration? if yes, ensure the above point no.2 is identical on both ends.