ZBT-WG2926 / MT7621 question

Currently I have a TPlink WDR4300. Tried running lede on it, and wireless crashes on it often for some reason. So right now I have it running the latest snapshot of openwrt. If anyone has input/experience with resolving the LEDE wirelessissue, please let me know.

Anyway, I was looking to upgrade. These MT7621 boards look pretty decent spec wise. Does anyone have experience with them on a LEDE image? Is it stable? Do all servers (samba, ftp Etc... ) work? Is wireless and network stability good? Lastly, how is the wireless coverage on it?

ZBT-WG2926 / MT7621

https://downloads.lede-project.org/snapshots/targets/ramips/mt7621/openwrt-ramips-mt7621-ew1200-squashfs-sysupgrade.bin

Would this be the correct image for the above router?

I'm using UniElec U7621-06 (256M RAM/16M flash) but I didn't buy their wireless cards.
I'm using my TP-LINK WN722N as wireless adapter.
Their original firmware PandoraBox is based on OpenWRT 14.09 and mainly targeted Chinese users.
PandoraBox's package repo links are down, probably a dead project?

So now I'm using OpenWrt SNAPSHOT r5647-9f62650

Is it stable?

No big problems so far except I have a ath9k_htc related warning in the kernel log continuously

[ 621.792698] ------------[ cut here ]------------
[ 621.797386] WARNING: CPU: 3 PID: 24 at net/sched/sch_hfsc.c:1400 0x8f17dd88
[ 621.804397] Modules linked in: ath9k_htc ath9k_common pppoe ppp_async ath9k_hw ath pppox ppp_generic nf_conntrack_ipv6 mac80211 iptable_nat ipt_REJECT ipt_MASQUERADE cfg80211 xt_time xt_tcpudp xt_tcpmss xt_statistic xt_state xt_recent xt_nat xt_multiport xt_mark xt_mac xt_limit xt_length xt_hl xt_helper xt_ecn xt_dscp xt_conntrack xt_connmark xt_connlimit xt_connbytes xt_comment xt_TCPMSS xt_REDIRECT xt_LOG xt_HL xt_DSCP xt_CT xt_CLASSIFY ums_usbat ums_sddr55 ums_sddr09 ums_karma ums_jumpshot ums_isd200 ums_freecom ums_datafab ums_cypress ums_alauda uas slhc nf_reject_ipv4 nf_nat_redirect nf_nat_masquerade_ipv4 nf_conntrack_ipv4 nf_nat_ipv4 nf_nat nf_log_ipv4 nf_defrag_ipv6 nf_defrag_ipv4 nf_conntrack_rtcache iptable_mangle iptable_filter ipt_ECN ip_tables crc_ccitt compat act_connmark nf_conntrack
[ 621.875134] act_skbedit act_mirred em_u32 cls_u32 cls_tcindex cls_flow cls_route cls_fw sch_tbf sch_htb sch_hfsc sch_ingress ip6t_REJECT nf_reject_ipv6 nf_log_ipv6 nf_log_common ip6table_mangle ip6table_filter ip6_tables x_tables ifb usb_storage ext4 jbd2 mbcache crc32c_generic mmc_block mtk_sd mmc_core leds_gpio xhci_mtk xhci_plat_hcd xhci_pci xhci_hcd ahci libahci libata sd_mod scsi_mod gpio_button_hotplug usbcore nls_base usb_common
[ 621.912650] CPU: 3 PID: 24 Comm: ksoftirqd/3 Tainted: G W 4.9.72 #0
[ 621.920013] Stack : 00000000 00000000 80567b4a 00000044 80411ca4 00000000 00000000 80560000
[ 621.928374] 8fca207c 804f9ea7 8048ef74 00000003 00000018 80563824 00000008 0000000a
[ 621.936735] 00000008 8006ab78 00000001 80560000 80500004 80500008 80493b80 8fcb3cd4
[ 621.945099] 00000003 800a9590 00000008 0000000a 81235e20 00000000 00000000 00cb3cd4
[ 621.953457] 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[ 621.961813] ...
[ 621.964255] Call Trace:
[ 621.966727] [<8000f814>] show_stack+0x54/0x88
[ 621.971081] [<801e78ac>] dump_stack+0x8c/0xd0
[ 621.975430] [<8002adc4>] __warn+0xe4/0x118
[ 621.979515] [<8002ae8c>] warn_slowpath_null+0x1c/0x30
[ 621.984583] [<8f17dd88>] 0x8f17dd88
[ 621.988126] ---[ end trace 6f609de93b76986f ]---

Do all servers (samba, ftp Etc… ) work?

Yes

Is wireless and network stability good? Lastly, how is the wireless coverage on it?

I'm using my USB wireless adapter as I said above.
About LAN performance.
image

I have never used a USB wireless card as an antenna. What is the range on those, as well as penetration through normal (non-brick) walls?