diff --git a/klippy/chelper/serialqueue.c b/klippy/chelper/serialqueue.c
index b6500fe621d5..e6810933aabc 100644
--- a/klippy/chelper/serialqueue.c
+++ b/klippy/chelper/serialqueue.c
@@ -62,6 +62,7 @@ struct serialqueue {
     int ready_bytes, upcoming_bytes, need_ack_bytes, last_ack_bytes;
     uint64_t need_kick_clock;
     struct list_head notify_queue;
+    double last_write_fail_time;
     // Received messages
     struct list_head receive_queue;
     // Fastreader support
@@ -376,8 +377,16 @@ do_write(struct serialqueue *sq, void *buf, int buflen)
         int ret = write(sq->serial_fd, &cf, sizeof(cf));
         if (ret < 0) {
             report_errno("can write", ret);
+            double curtime = get_monotonic();
+            if (!sq->last_write_fail_time) {
+                sq->last_write_fail_time = curtime;
+            } else if (curtime > sq->last_write_fail_time + 10.0) {
+                errorf("Halting reads due to CAN write errors.");
+                pollreactor_do_exit(sq->pr);
+            }
             return;
         }
+        sq->last_write_fail_time = 0.0;
         buf += size;
         buflen -= size;
     }
diff --git a/src/stm32/usbfs.c b/src/stm32/usbfs.c
index d166fbb7ace9..ad2e7b3eb56e 100644
--- a/src/stm32/usbfs.c
+++ b/src/stm32/usbfs.c
@@ -236,7 +236,8 @@ usb_read_bulk_out(void *data, uint_fast8_t max_len)
     return count;
 }
 
-static uint32_t bulk_in_push_count, bulk_in_pop_flag;
+static uint32_t bulk_in_push_pos, bulk_in_pop_flag;
+#define BI_START 2
 
 int_fast8_t
 usb_send_bulk_in(void *data, uint_fast8_t len)
@@ -245,8 +246,8 @@ usb_send_bulk_in(void *data, uint_fast8_t len)
         // No buffer space available
         return -1;
     uint32_t ep = USB_CDC_EP_BULK_IN;
-    int bufnum = bulk_in_push_count & 1;
-    bulk_in_push_count++;
+    uint32_t bipp = bulk_in_push_pos, bufnum = bipp & 1;
+    bulk_in_push_pos = bipp ^ 1;
     btable_write_packet(ep, bufnum, data, len);
     writel(&bulk_in_pop_flag, USB_EP_DTOG_RX);
 
@@ -254,7 +255,18 @@ usb_send_bulk_in(void *data, uint_fast8_t len)
     uint32_t epr = USB_EPR[ep];
     if (epr_is_dbuf_blocking(epr) && readl(&bulk_in_pop_flag)) {
         writel(&bulk_in_pop_flag, 0);
-        USB_EPR[ep] = calc_epr_bits(epr, 0, 0) | USB_EP_DTOG_RX;
+        if (unlikely(bipp & BI_START)) {
+            // Two packets are always sent when starting in double
+            // buffering mode, so wait for second packet before starting.
+            if (bipp == (BI_START | 1)) {
+                bulk_in_push_pos = 0;
+                writel(&bulk_in_pop_flag, USB_EP_KIND); // Dummy flag
+                USB_EPR[ep] = calc_epr_bits(epr, USB_EPTX_STAT
+                                            , USB_EP_TX_VALID);
+            }
+        } else {
+            USB_EPR[ep] = calc_epr_bits(epr, 0, 0) | USB_EP_DTOG_RX;
+        }
     }
 
     return len;
@@ -319,9 +331,8 @@ usb_set_configure(void)
     USB_EPR[ep] = calc_epr_bits(USB_EPR[ep], USB_EPRX_STAT, USB_EP_RX_VALID);
 
     ep = USB_CDC_EP_BULK_IN;
-    bulk_in_push_count = 0;
+    bulk_in_push_pos = BI_START;
     writel(&bulk_in_pop_flag, 0);
-    USB_EPR[ep] = calc_epr_bits(USB_EPR[ep], USB_EPTX_STAT, USB_EP_TX_VALID);
 }
 
 
@@ -342,12 +353,12 @@ usb_reset(void)
 
     ep = USB_CDC_EP_BULK_OUT;
     USB_EPR[ep] = (USB_CDC_EP_BULK_OUT | USB_EP_BULK | USB_EP_KIND
-                   | USB_EP_RX_VALID | USB_EP_TX_NAK | USB_EP_DTOG_TX);
+                   | USB_EP_RX_NAK | USB_EP_DTOG_TX);
     bulk_out_push_flag = USB_EP_DTOG_TX;
 
     ep = USB_CDC_EP_BULK_IN;
     USB_EPR[ep] = (USB_CDC_EP_BULK_IN | USB_EP_BULK | USB_EP_KIND
-                   | USB_EP_RX_NAK | USB_EP_TX_NAK);
+                   | USB_EP_TX_NAK);
     bulk_in_pop_flag = USB_EP_DTOG_RX;
 
     USB->CNTR = USB_CNTR_CTRM | USB_CNTR_RESETM;