Income Taxes - Schedule of Components of Deferred Tax Assets and Deferred Tax Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Deferred tax assets (liabilities):
Capitalized inventory costs	$ 204	$ 168
Inventory write-downs	991	2,856
Accrued warranty	53	161
Deferred profits	1	346
Accruals and reserves not currently deductible	2,913	3,531
Stock option expense	806	849
Federal net operating loss carryforwards	18,445	6,979
Foreign and state net operating losses	231	10,481
Book vs. tax depreciation and amortization	(1,465)	(1,546)
Other deferred tax assets	120	75
Total deferred tax assets	22,299	23,900
Valuation allowance	(21,733)	(23,900)	$ (23,769)
Deferred tax assets, net of valuation allowance	$ 566	$ 0