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I use UNIT CAMERA DIY KIT.
I tested it with the latest cameraWebServer sample program.
I got the same error, so I checked the source program.
I found the following description in the comment of esp_camera.h.

typedef enum {
CAMERA_FB_IN_PSRAM, / *! <Frame buffer is placed in external PSRAM * /
CAMERA_FB_IN_DRAM / *! <Frame buffer is placed in internal DRAM * /
} camera_fb_location_t;

I added one line to the cameraWebServer program as a trial.

// if PSRAM IC present, init with UXGA resolution and higher JPEG quality
// for larger pre-allocated frame buffer.
if (psramFound ()) {
config.frame_size = FRAMESIZE_UXGA;
config.jpeg_quality = 10;
config.fb_count = 2;
} else {
config.frame_size = FRAMESIZE_SVGA;
config.jpeg_quality = 12;
config.fb_count = 1;
config.fb_location = CAMERA_FB_IN_DRAM; // add 2021-12-09
}

I checked the operation of UNIT CAM.

12: 48: 08.541-> ets Jul 29 2019 12:21:46
12: 48: 08.541->
12: 48: 08.541-> rst: 0x1 (POWERON_RESET), boot: 0x13 (SPI_FAST_FLASH_BOOT)
12: 48: 08.541-> configsip: 0, SPIWP: 0xee
12: 48: 08.541-> clk_drv: 0x00, q_drv: 0x00, d_drv: 0x00, cs0_drv: 0x00, hd_drv: 0x00, wp_drv: 0x00
12: 48: 08.541-> mode: DIO, clock div: 1
12: 48: 08.541-> load: 0x3fff0030, len: 1420
12: 48: 08.587-> ho 0 tail 12 room 4
12: 48: 08.587-> load: 0x40078000, len: 13540
12: 48: 08.587-> load: 0x40080400, len: 3604
12: 48: 08.587-> entry 0x400805f0
12: 48: 08.821->
12: 48: 09.675-> ...........
12: 48: 14.695-> WiFi connected
12: 48: 14.695-> Camera Ready! Use'http://192.168.1.220' to connect