Setup: Original Prusa MK4S (fw 6.5.7) and CORE One L (fw 6.8.1). Both on Wi-Fi, both monitored via PrusaLink from Home Assistant. Ethernet isn't an option due to their location.
Both of these printers were purchased preassembled. I don't believe this issue happened at all before I for my Unify network. I use a Unifi Cloud Gateway Ultra and U6 Pro.
Symptoms come in two flavors:
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Drops that recover: Each printer drops off Wi-Fi roughly once every two hours and comes back on its own. Recovery times are weirdly quantized — out of 304 logged outages they land at ~31s, ~62s, or ~93s and almost nothing in between. Looks like 1/2/3 passes of a fixed retry loop. This matches Buddy #5152 (ESP32 NIC does a probe-scan after 5s of no inbound traffic, gives up after N retries).
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Drops that don't. About 7–11% of the time the retry never completes and the printer just stays off. Go to the Wi-Fi wizard and it says "no network card." The board can't see the ESP module at all, so toggling Wi-Fi does nothing, because there's nothing to toggle. Only a power cycle brings it back. This is the bigger issue. Before I automated the toggle the printers would remain offline until I started my next print. The automation works, checking the printers last state before toggling, but I do fear it interrupting a print in progress and would prefer a more permanent solution.
What I've ruled out:
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Signal. A Raspberry Pi camera (that used to be OctoPi) and a wifi smart plug sit in the same room, same AP, same 2.4 GHz band. 100% stable for 9+ days while both printers were dropping constantly. Printer RSSI is -69 to -75 dBm, SNR 21–24 dB, associating at 57–72 Mbps.
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Access point settings. UniFi U6 Pro. PMF disabled, WPA2 only, no WPA3, 802.11r off, BSS transition off, multicast enhancement off, minimum data rate on auto. Tried both printers on multiple SSIDs with different combinations of all of the above.
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Channel / congestion. Also unrelated: separate network work here (killing an mDNS reflector) measurably improved the rest of my Wi-Fi without changing the wifi drop rate.
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Power. Both printers on metered smart plugs, continuous draw through every outage. They're on, just off-network.
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Firmware. Both were on 6.5.3; I flashed 6.5.7 / 6.8.1 by USB (which also rewrites the ESP firmware). Zero change. Same 2-hour cadence, same 31/62/93s quantization, same wedge rate.
Has anyone else seen the "no network card" variant specifically? https://github.com/prusa3d/Prusa-Firmware-Buddy/issues/5152 describes flapping, not the module disappearing off the board's own bus. I can't find a report of this.
Did reseating or replacing the ESP module fix it for you? Two printers failing identically makes hardware feel unlikely to me.
Anything else worth testing before I open a new issue?
Source: r/prusa3d · by /u/Darklyte