Checked if IMMT1T QPD would have reponse even when IMC unlocked, and yes, it seemed so.

Detailes

According to the past data, IMMT1T had 12800 counts when IMC locked at around 1W. According to the wikipage, MCi and MCo have transmittance of 0.6% each, so the total transmittance when IMC unlocked should be around 3.6e-5. Assuming that the transmittance of IMC locked would be around 1, currently 12800 counts * 3.6e-5 = 0.5 counts should be found, and the attached figure would imply that the IMMT1T QPD would respond to this faint light (referring MCi reflection light caught by IMC_REFL), and this would imply the unlocked optical axis would be still kept. Maybe good news...

Hope this would not be due to room light....