Hi,
please see below a feedback I got from Apps team...
Q: But, If slave is powered ON and Master is in sleep mode. Our slave goes to sleep after 4 seconds(timeout), Now, If we start the transmission from master, slave is not responding. If we start the transmission within 4 seconds then slave is responding as expected.
[Diep] According to the lin spec, because the slave node goes to sleep mode, so the master node must send a wake-up signal before sending any frames on the bus.
Please refer chapter 2.6 of LIN_Specification_Package_2.2A.pdf for more detail.

If the issue is still not resolved, please share your project and then I will try to check on my site.
BR, Petr