LNK306 restart problem with optocoupler feedback

Hello,

I'm currently designing a 250mA, 24VDC power supply using the LNK306 with optocoupler feedback.
Experimentally, the circuit works fine, I've about 24VDC in no-load and small load conditions (about <60mA).

However, I've a to supply a 24VDC brushless fan (Sunon MF40202VX), which pulls 180mA briefely and consume about 80mA when spinning.
When the fan is connected, the output voltage of the circuit drops to almost 0V, and the LNK306 seems to restart every second or so, and never reach my desired output voltage.

Also, I cannot figure out how to soft-start the LNK306 for high output capacitances. AN-37 specifies how to do that on direct feedback but not with opto feedback.

Please, help me :)