Tigo TS4-A-2F causing 'late start' on cold mornings ?

[dtbaker61]

Very mysterious problem I am having with an offgrid install using:
- string of 8 Qcell 400w modules with 4 Tigo TS4-A-2F RSD units
- run to a ISO pv isolator switch , transition to EMT, and run inside to a nice warm garage
- Sol-ark 8k-outdoor with Tigo RX and stack of four ed4-LL batteries are inside warm garage

everything runs fine when night-time temps are above freezing. pv voltage comes up from 2v to 250+ and production ramps up

when overnight temp drops below freezing.... PV voltage goes from around 2v overnight, to around 5v at sunrise and gets 'stuck' rather than continuing to rise to operating voltage. An hour, or two, or three after sunrise, voltage jusmp up to 'normal' 300v or so and production begins.

Tigo RX is getting 12v from 120vAC Load power via Tigo 1A power supply
Sol-ark, Tigo RX, batteries are all warm in garage

QUESTIONS:

1. has anybody else had 'late starts' with Tigo -2F RSD units on cold mornings ?

2. Is it POSSIBLE that ISO switch (with breakers inside) could mess up RX signal when cold, and then be ok when warm ?