diff --git a/app/client/ui/AdminPanel.ts b/app/client/ui/AdminPanel.ts
index e2cc38bf01..0b1e540410 100644
--- a/app/client/ui/AdminPanel.ts
+++ b/app/client/ui/AdminPanel.ts
@@ -202,7 +202,10 @@ Please log in as an administrator.`)),
         const success = result?.status === 'success';
         const details = result?.details as SandboxingBootProbeDetails|undefined;
         if (!details) {
-          return cssValueLabel(t('unknown'));
+          // Sandbox details get filled out relatively slowly if
+          // this is first time on admin panel. So show "checking"
+          // if we don't have a reported status yet.
+          return cssValueLabel(result?.status ? t('unknown') : t('checking'));
         }
         const flavor = details.flavor;
         const configured = details.configured;
diff --git a/app/server/MergedServer.ts b/app/server/MergedServer.ts
index ba307e8060..2ac994d169 100644
--- a/app/server/MergedServer.ts
+++ b/app/server/MergedServer.ts
@@ -192,12 +192,6 @@ export class MergedServer {
       this.flexServer.checkOptionCombinations();
       this.flexServer.summary();
       this.flexServer.ready();
-
-      // Some tests have their timing perturbed by having this earlier
-      // TODO: update those tests.
-      if (this.hasComponent("docs")) {
-        await this.flexServer.checkSandbox();
-      }
     } catch(e) {
       await this.flexServer.close();
       throw e;
diff --git a/app/server/lib/BootProbes.ts b/app/server/lib/BootProbes.ts
index 36c3786c56..df0f202efd 100644
--- a/app/server/lib/BootProbes.ts
+++ b/app/server/lib/BootProbes.ts
@@ -265,7 +265,7 @@ const _sandboxingProbe: Probe = {
   id: 'sandboxing',
   name: 'Is document sandboxing effective',
   apply: async (server, req) => {
-    const details = server.getSandboxInfo();
+    const details = await server.getSandboxInfo();
     return {
       status: (details?.configured && details?.functional) ? 'success' : 'fault',
       details,
diff --git a/app/server/lib/FlexServer.ts b/app/server/lib/FlexServer.ts
index 4bdf536916..4d39cb1c09 100644
--- a/app/server/lib/FlexServer.ts
+++ b/app/server/lib/FlexServer.ts
@@ -1386,8 +1386,9 @@ export class FlexServer implements GristServer {
     }
   }
 
-  public async checkSandbox() {
-    if (this._check('sandbox', 'doc')) { return; }
+  public async getSandboxInfo(): Promise<SandboxInfo|undefined> {
+    if (this._sandboxInfo) { return this._sandboxInfo; }
+
     const flavor = process.env.GRIST_SANDBOX_FLAVOR || 'unknown';
     const info = this._sandboxInfo = {
       flavor,
@@ -1397,6 +1398,8 @@ export class FlexServer implements GristServer {
       sandboxed: false,
       lastSuccessfulStep: 'none',
     } as SandboxInfo;
+    // Only meaningful on instances that handle documents.
+    if (!this._docManager) { return info; }
     try {
       const sandbox = createSandbox({
         server: this,
@@ -1421,10 +1424,7 @@ export class FlexServer implements GristServer {
     } catch (e) {
       info.error = String(e);
     }
-  }
-
-  public getSandboxInfo(): SandboxInfo|undefined {
-    return this._sandboxInfo;
+    return info;
   }
 
   public getInfo(key: string): any {
diff --git a/app/server/lib/GristServer.ts b/app/server/lib/GristServer.ts
index 23feb8c03c..e6bd1fa27e 100644
--- a/app/server/lib/GristServer.ts
+++ b/app/server/lib/GristServer.ts
@@ -69,7 +69,7 @@ export interface GristServer {
   servesPlugins(): boolean;
   getBundledWidgets(): ICustomWidget[];
   getBootKey(): string|undefined;
-  getSandboxInfo(): SandboxInfo|undefined;
+  getSandboxInfo(): Promise<SandboxInfo|undefined>;
   getInfo(key: string): any;
 }
 
@@ -163,7 +163,7 @@ export function createDummyGristServer(): GristServer {
     getPlugins() { return []; },
     getBundledWidgets() { return []; },
     getBootKey() { return undefined; },
-    getSandboxInfo() { return undefined; },
+    getSandboxInfo() { return Promise.resolve(undefined); },
     getInfo(key: string) { return undefined; }
   };
 }