Can I use mqtt use sent seval downlink messages to the same Class C device?

Hi, everyone!

I found that when my pragram sent seval downlink message to NS, only one or two can be recieved by the device. But if I sent it one by one with an interval about 300ms, they all will be recieved by the device. Is there any config can be used to solve the problem?

# Class-C settings.
# Downlink lock duration
# Contains the duration to lock the downlink Class-C transmissions
# after a preceeding downlink tx (per device).

Is above config useful?

What is the Class C timeout value in your device-profile?