Qualcomm Atheros AR9160 crash:DMA failed to stop in 10

I use board Alix3d3 with 2 pcs mpci wificard AR9160 on Openwrt 18.06.1.
At first everything looks fine. One wifi card is placed in 2.4 other in 5 GHz.
When he loads any card more than 20 mbps it crashes.
The console starts flooding with messages:

[78018.158821] ath: phy0: DMA failed to stop in 10 ms AR_CR=0x00000024 AR_DIAG_SW=0x42100020 DMADBG_7=0x00006040
[78018.363541] ath: phy0: DMA failed to stop in 10 ms AR_CR=0x00000024 AR_DIAG_SW=0x42100020 DMADBG_7=0x00006040
[78018.568140] ath: phy0: DMA failed to stop in 10 ms AR_CR=0x00000024 AR_DIAG_SW=0x42100020 DMADBG_7=0x00006040
[78018.772902] ath: phy0: DMA failed to stop in 10 ms AR_CR=0x00000024 AR_DIAG_SW=0x42100020 DMADBG_7=0x00006040
[78018.977536] ath: phy0: DMA failed to stop in 10 ms AR_CR=0x00000024 AR_DIAG_SW=0x42100020 DMADBG_7=0x00006040
[78019.182297] ath: phy0: DMA failed to stop in 10 ms AR_CR=0x00000024 AR_DIAG_SW=0x42100020 DMADBG_7=0x00006040

The problem is resolved after restarting the radio with

wifi restart radioX

to the next load of more than 20 mbps.

I will be grateful to anyone who has given me direction to make my devices usable.