Gemma M0, A1 NeoPixel strip, 8 pixels max

[ricknun]

Describe the bug
Gemma M0 driving a NeoPixel strip on pin A1 has a limit of 8 NeoPixels max.

To Reproduce
Connect an Adafruit 3811 30-NeoPixel strip to Gemma M0 (black to GND, red to Vout, white to A1). Download the program shown and see 8 NeoPixels on the strip blink (good). Change the number of pixels from 8 to 9 and download the program. See Morse Code "SOS" on the Gemma LED and no action on the NeoPixel strip (bad).

Expected behavior
At least 30 NeoPixels should be supported, similar to using pin A0 (that works fine).

Desktop (please complete the following information):

• OS: Windows 10
• Firefox 130.0 (64-bit) at https://maker.makecode.com/#editor

Additional context
The problem doesn't have to do with supply current. It happens at max current (RGB = 0xffffff) and low current (RGB = 0x200000). The problem occurs on pin A1 but using pin A0 instead works fine, allowing all 30 pixels in the strip to blink.