Received the light yesterday…
-only one high mode.
-whines and whistles every once in a while.
-it now blinks intermittently.
What a I missing?
Thinking back to issues in the past 
I remember that
if the black lead to the ledboard makes contact with body or reflector it puts a C8 in direct drive (turbo).
I don’t know if your light is glued, but if I were you, I would check that out.
You might not notice it at first glance, but the same can happen with a lead with damaged insulation.
Intermittend blinking: in a certain frequency, or every now and then. Could be bad soldering of driver.
Intermittent blinking, could you be more specific?
The XT45 does feature LVP where it will blink intermittently, what might be the cause.
However, it should have 3 or 4 modes
blinking intermittently sounds like LVP to me… one high mode sounds like what Henk was saying, grounding failure/etc… ive had that happen when resoldering mcpcb before… makes me hesitant to buy this light as it was on my list… cool design
My light also arrived with only a high mode. Here is how you may get different modes. ( Pardon the errors, this was typed from my phone.)
Turn the flashlight on and half click the button five times. The flashlight will then be in mode selection. It will flash once then twice and so on. When it flashes the number of times corresponding to the mode you want, then half press the button to save it.
One flash mode: High only
Two flashes mode: low and high
Three flashes mode: appears to also be low and high
Four flashes mode: low - medium - high
Five flashes mode: low - medium - medium high - high
*Turbo is always a double half click
Now, I only have two modes after recharging the battery. Weird
That sounds like a good tip!
I got the V1, i know they released a V2 with an updated UI.
On their site they do describe V2