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Product Warranties (Details) - Schedule of Product Warranty Liability - USD ($)
$ in Thousands
12 Months Ended
Apr. 30, 2020
Apr. 30, 2019
Schedule of Product Warranty Liability [Abstract]    
Balance at beginning of year $ 529 $ 520
Warranty costs incurred (293) (398)
Product warranty accrual 291 407
Balance at end of year $ 527 $ 529